So they tried little games, like placing a dot in the patient's left visual field, followed by a dot in their right visual field.
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How does the installation situate itself in this visual field?
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People see jagged lights or have blind spots in their visual field.
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At times, patients can see flashing lights or stars in their visual field.
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The ball should move through the center of your visual field, temporarily occluding the target.
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Others have trouble focusing their eyes or a part of their visual field goes blurry.
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Visual information appearing in UD's left visual field now has "nowhere to go," explained Behrmann.
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This allowed them to reconstruct the visual field of the wasp, and of their home in particular.
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When a beautiful game like Battlefield V suddenly looks like Minecraft, the visual field becomes less cluttered.
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It projects a rectangle of red text and icons down in the lower right of your visual field.
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Once you start a movie or show, the content takes up a large percentage of your visual field.
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Blurred vision that doesn't improve in one or both eyes, especially the central part of your visual field.
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Artists can respond by reflecting and distorting this new visual field, like the painters Jacqueline Humphries and Laura Owens.
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"You may think of the brain as taking a photograph of what you see in your visual field," Young said.
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You zoom in and out of the screen, panning across this massive scene, combing the visual field for these little goofy things.
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The footnote at the bottom of the visual field corresponds to the number one hovering just above the letter "k" in "THEBLACK".
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Distance unified the fragments into a single visual field; proximity revealed its actual lack of fixity and the temporality of its cohesion.
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As human beings, we recognize a face or an object regardless of where in our visual field (or in a picture) it appears.
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He constantly rearranges this visual field, adding to it or subtracting from it, so that the blimp records something different during every flight.
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The bands and stripes of color play a role in this, activating the visual field, while the interacting shapes create the illusion of movement.
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A third way is augmented reality, in which the machine improves a person's visual field, and gives them information while they're doing something else.
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Both sides of the brain process vision, but the left hemisphere is responsible for the right side of our visual field, and vice versa.
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The M.R.I. scan later that day showed that I indeed had a small brain tumor that was bleeding and blocking my right visual field.
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Nearly all the shapes are done in gray, with a few black and pale, nearly white ones scattered throughout the painting's teeming visual field.
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Trevor wanted to look at the impact of artificial intelligence technology on the visual field, so I invited him to spend time at Stanford.
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The electrodes are then "all linked in real-time so that any movement in the visual field launches a synchronized GVS command," according to Cevette.
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Some patients with ocular melanoma have symptoms similar to a detached retina — flashes of light, floaters in their visual field, and visual deficits, said Orloff.
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It happens first with footage of a young girl tracing lines in the dirt path with a knife before throwing the knife across your visual field.
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Even if we don't say out loud that failing vision has something to do with our vastly narrowed visual field, our bodies seem to know what's up.
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It receives light from the outside world and projects a scale replica of our visual field onto the retina, which sits in the back of the eye.
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During Tate Modern's 2013 Global Pop symposium much of the discussion concerned the emergence, during the 20th century, of a worldwide "monoculture," particularly in the visual field.
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I noticed hairstylists and makeup artists were uploading 15-second clips and before-and-after transformations of their work, and I thought, Dermatology is a really visual field.
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It is not possible to go completely blind from looking at the eclipse, Chou said, because the injury is limited to the central part of your visual field.
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The bad guy is essentially a villainous video game executive who wants to sell tiered memberships to the Oasis and populate people's visual field with pop up ads.
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The classic example is zig-zagging lights off to one side of your visual field that gradually become larger and more intense (also known as a visual aura).
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Doctors define legal blindness as central visual acuity of 23/33 or less with the best possible correction, and/or a visual field of 23 degrees or less.
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LGN cells send a pulse to the visual cortex when they detect a change from dark to light, or vice versa, in their tiny section of the visual field.
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The main challenge when I'm scuba diving is that my visual field is limited, because you're wearing a mask where you can't see far to the left or right.
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The light also has to take up a lot of the person's visual field — a little light in the distance isn't going to be a problem, Dr. French added.
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Predicting pixels—that is, using deep learning and computer vision to model an agent's visual field in its entirety from moment to moment—makes it hard to filter out potential distractions.
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If several edges and circles come together to make a face, you don't care exactly where the face is found in the visual field; you just care that it's a face.
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The strangeness of the visuals also suggests the freezing of time; the viewer can see, in one frame, both the visual field of a few seconds ago and of the present.
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In human visual perception, this is reflected by the fact that a cluster of neurons is focused on a small receptive field, which is part of the much larger entire visual field.
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Quick shifts of direction and geometric patterning dominate this first section; Ms. Childs's characteristic use of stillness and rapid movement for alternating groups keeps the visual field utterly clear and spatially surprising.
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Currently Young, Shapley, and Chariker are working on adding directional sensitivity into their model—which would explain how the visual cortex reconstructs the direction in which objects are moving across your visual field.
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The installation is a powerfully emotive record of the destruction in the region — made worse by corruption and governmental ineptitude — with a a fault line violently rupturing the piece's otherwise smooth visual field.
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Visual snow, or the appearance of a grainy texture throughout the visual field, is neuronal, having to do more with how neurons and nerves process signals, than with the structure of the eye itself.
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The man also told the doctors, who eventually authored the case report, that he had symptoms like fatigue, irritation in his right eye, and a blind spot in the center of his visual field.
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In a new study in Current Biology, Painter and his colleagues looked to see if people with Charles Bonnet Syndrome had overactive responses to the intact parts of their visual field, even when they weren't hallucinating.
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On the other hand, a study that examined how people encoded the shapes and colors of abstract objects in their visual field would be less likely to vary if it were rerun at another place and time.
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The platform uses convolutional neural networks—a machine term for a forward-fed artificial neural network where neuron connectivity patterns respond to overlapping regions in the visual field—in order to enhance photo patterns with surreal effects.
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On average, it takes fifteen seconds for WD's brain to catch up with his eyes—the center of his visual field is harder still—but when Jerpe shined the light through the outstretched Slinky, WD's gaze snapped to it.
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The mirrored rooms, where reflections within reflections seem to forever extend the visual field, play with these themes, from an early 1965 example (recreated this year) that makes a mountain of the phallus forms to a 2016 pumpkin extravaganza.
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"We saw damage, a change in the center part of her retina, which corresponds with your central visual field, and that is a tipoff for us that there was something going on here related to the eclipse," Deobhakta said.
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Though they are experienced through the eyes, the changes that wreak havoc on the visual field are actually caused by a phenomenon that takes place in the back of the brain, where the visual cortex is located, Krel said.
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As children, the subjects used central vision to focus on the on-screen characters, and the images would have generally been held in front of the face, making them about the same size in the visual field across subjects.
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Symptoms vary by person but generally include blurry vision, spots in the visual field and vision loss, according to Dr. Marlana Orloff, an oncologist at Jefferson University Hospitals in Philadelphia, who is treating a number of the people in the Alabama group.
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Until Stephen Shore began making his color photos of breakfasts, beds, intersections, parking lots and just about everything else that drifted into his visual field, no one else annotated the banal surfaces of American life with quite the same level of unjudgmental aplomb.
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With that in mind, we've decided to team up with London based illustrator Josh Hanton to produce a kind of visual field guide to the absolute worst people you'll definitely meet at a festival at some point over the next few months.
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The theory suggests that the dimensions and locations of brain regions devoted to visual stimuli are defined by the amount of space in the visual field that those images consume, as well as whether they are primarily observed in a subject's central or peripheral vision.
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"We can reduce neural interference and improve people's ability to recognize images even when they are presented at a rate of 12 per second by alternating which side of the visual field we show subsequent stimuli to," said the study's senior investigator Maximilian Riesenhuber, PhD, a professor of neuroscience at Georgetown.
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To summarize: "the colors were composing to create a whole," geometric Flower of Life patterns took over my visual field and peaceful sadness leaked from my eyes as I listened to Frank Ocean's Blonde, every note on the record synergizing with the wholesomeness of reality filtered through a heightened empathy.
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By compressing spiky forms into the veined skin of decalcomania, the technique of transferring wet paint onto a surface from a sheet of paper, or sharp-edged transparent planes into a granular black ground, Kaiser is able to bring order and violence, symmetry and dissolution, semi-transparent edges and depthlessness into the same visual field.
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Because you don't know where the relevant features will appear, you have to scan the entire visual field, either sequentially, sliding your small receptive field as a window over it (top to bottom and left to right) or have multiple smaller receptive fields (clusters of neurons) that each focus on (overlapping) small parts of the input.
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"Anne Treisman's major contribution was to show that basic visual properties like color and motion can be perceived over the whole visual field at once, but combinations of these properties can only be correctly perceived by inspecting each object in turn," said Nancy Kanwisher, a professor of cognitive neuroscience at the Massachusetts Institute of Technology who did her postdoctoral work under Dr. Treisman.
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"Every Which Way" seems to have made a virtue out of its differences with that masterstroke of art and engineering, coming on lightly with a clarity of space and scale: the black slabs stand in a stately progression, cutting deeply into the visual field presented by the room's white walls, with the gaps in between feeling as crisp as Alpine air.
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My Ogre Book alludes to card games and chess, but these references fit with the hothouse artificiality of the book's figures and conceits; in Midnight Broodthaers collages sound-words ("Tic Tac Tic Tac Tic") and strings of spelled-out numbers into his poems, so that the page not only records the poetic utterance but becomes a visual field to be worked upon, played with.
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By the late 2109s, with works such as "Boston" (2210, 22004 x 19373 inches; all works oil on canvas) and "Whelan" (19607, 21987 x 287 inches), Resnick had arrived at a distinctive approach to his generation's existential confrontation with the void of the canvas — an insistent, fluttering brushstroke sustained across the entire visual field, shifting dramatically in hue but not by much in scale.
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Perimetry or campimetry is one way to systematically test the visual field. It is the systematic measurement of differential light sensitivity in the visual field by the detection of the presence of test targets on a defined background. Perimetry more carefully maps and quantifies the visual field, especially at the extreme periphery of the visual field. The name comes from the method of testing the perimeter of the visual field.
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Common problems of the visual field include scotoma (area of reduced vision), hemianopia (half of visual field lost), homonymous hemianopsia and bitemporal hemianopia.
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When the patient's right eye is being tested, closing the other eye, patient is instructed to look directly at the examiners left eye. Examiner closes his/her left eye, and then conduct finger movements, bringing his/her fingers or any other into your visual field from the sides. Since the test is basically comparison of the patient's visual field with the examiner's visual field, it is not an accurate measument of visual field.
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The campimeter is an instrument for examining the visual field. Campimeters have been in clinical use since the mid-nineteenth century. Initially, examination of the visual field was concerned only with the outer limits, or 'perimeter' of the visual field, hence the term 'perimetry', which tends to be used inter-changeably with 'campimetry'.
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Thus, for the first set of trials, participants may pay attention to the right visual field, but subsequently they may pay attention to the left visual field. Within each trial and across visual fields, participants are presented with the same stimuli, for example flashes of lights varying in duration. Participants are told that when a particular stimulus, such as a short duration flash of light, referred to as a target, appears in the visual field they are attending, they should respond with a button press. The number of targets within each visual field is less than that number of non-targets, and participants are also told to ignore the other visual field and to not respond to the targets presented in that visual field.
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The calcarine sulcus is where the primary visual cortex (V1) is concentrated. The central visual field is located in the posterior portion of the calcarine sulcus and the peripheral visual field in the anterior portion.
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The divided visual field paradigm capitalizes on the lateralization of the visual system. Each cerebral hemisphere only receives information from one half of the visual field—specifically, from the contralateral hemifield. For example, retinal projections from ganglion cells in the left eye that receive information from the left visual field cross to the right hemisphere at the optic chiasm; while information from the right visual field received by the left eye will not cross at the optic chiasm, and will remain on the left hemisphere.Jeffery, G. (2001).
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Visual field, restricted vision and sheep movement in laneways. Appl. Anim. Ethol. 6: 175–187. although photographs of the experiments indicate that only limited facial wool regrowth had occurred since shearing. In addition to facial wool (in some breeds), visual field limitations can include ears and (in some breeds) horns, so the visual field can be extended by tilting the head.
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Measurements of visual field defects can be done by visual field testing. It can be performed by various methods, including confrontation technique, amsler grid, tangent screen, kinetic perimetry, or static perimetry. Cost common is automated perimetry.
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Note that eye movements are excluded in the definition. Different animals have different visual fields, depending, among others, on the placement of the eyes. Humans have a slightly over 210-degree forward-facing horizontal arc of their visual field, while some birds have a complete or nearly complete 360-degree visual field. The vertical range of the visual field in humans is around 150 degrees.
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However, these methods are significantly more costly than the divided visual field paradigm.
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When one of these pathways is damaged, the corresponding visual field is lost.
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Multifocal techniques are used in electroretinogram and visual evoked potential recordings to separate the responses originating from the stimulation of different locations in the visual field (and thus different retinal locations). The concept is as follows: Each visual field location is stimulated with a stimulus sequence that is uncorrelated to the sequences used for the other locations. All visual field locations are stimulated in parallel with their individual stimulus sequence. The retinal or cortical activity, which is a mixture of the responses from all visual field locations, is recorded with usual electroretinographic or visual evoked potential methods, respectively.
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Usually referred to as SITA, the Swedish interactive thresholding algorithm is a method to test for visual field loss, usually in glaucoma testing or monitoring. It is combined with a visual field test such as standard automated perimetry (SAP) or short wavelength automated perimetry (SWAP) to determine visual fields in a more efficient manner. Standard automated perimetry determines how dim of light (the threshold) can be seen at various points in an individual eye's visual field. Various algorithms have been developed to determine this threshold in the dozens to over a hundred individual points in a single visual field.
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The C1 component is sensitive to where a stimulus is presented in a visual field (Jeffreys and Axford, 1965). The C1 has been shown to be negative when items are presented in the top half of the visual field and positive when the visual stimuli are presented in the bottom half of the visual field. The scalp distribution of the C1 component can also lateralized based on the lateralization of the stimuli (Jeffreys & Axford, 1964). Stimuli presented in the left half of the visual field will elicit more negativity over the rightward occipital and parietal channels.
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For both eyes the combined visual field is 130–135° vertically and 200–220° horizontally.
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The range of visual abilities is not uniform across the visual field, and varies from animal to animal. For example, binocular vision, which is the basis for stereopsis and is important for depth perception, covers 114 degrees (horizontally) of the visual field in humans; the remaining peripheral 40 degrees on each side have no binocular vision (because only one eye can see those parts of the visual field). Some birds have a scant 10 to 20 degrees of binocular vision. Similarly, color vision and the ability to perceive shape and motion vary across the visual field; in humans color vision and form perception are concentrated in the center of the visual field, while motion perception is only slightly reduced in the periphery and thus has a relative advantage there.
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A scotoma often occurs when the visual disturbance moves to the periphery of the visual field. Additionally, a scotoma can sometimes occur in the center of the visual field which will appear as a more distinct blindspot, although this is less common. Individuals with persistent MA may also report a visual disturbance called 'visual snow'. Generally, they will describe their visual field as consisting of many small flickering spots which may resemble snow.
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Consequently, visual performance variations across the visual field can often be equalized by enlarging stimuli depending on their location in the visual field by a factor that compensates for cortical magnification, which is referred to as M scaling (M=magnification). However, the variation of visual performance across the visual field differs widely between different functions (pattern recognition, motion perception, etc.), and cortical magnification is only one factor amongst others that determine visual performance.
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The predominant theory on the red appearing in the visual field is not due to the actual blood flow to the eye. It is most likely due to the blood laden lower eyelid coming into the visual field due to the pull of negative-Gs.
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The false images can occur in any part of the visual field, and are rarely polymodal.
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In severe cases, it may obstruct as much as 50 percent of the superior visual field.
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The monkeys performed very similar to human participants and were unable to perceive the presence of stationary objects outside of their visual field. Another 1995 study by the same group sought to prove that monkeys could also be conscious of movement in their deficit visual field despite not being consciously aware of the presence of an object there. To do this, researchers used another standard test for humans which was similar to the previous study except moving objects were presented in the deficit visual field. Starting from the center of the deficit visual field, the object would either move up, down, or to the right.
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When a person views something in the left visual field (that is on the left side of their body), the information travels to the right hemisphere of the brain and vice versa. In the first series of tests, Sperry would present a word to either the left or right visual field for a short period of time. If the word was shown to the right visual field, meaning the left hemisphere would process it, then the patient could report seeing the word. If the word was shown to the left visual field, meaning the right hemisphere would process it, then the patient could not report seeing the word.
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In more specific terms, fibers carrying information from the contralateral superior visual field traverse Meyer's loop to terminate in the lingual gyrus below the calcarine fissure in the occipital lobe, and fibers carrying information from the contralateral inferior visual field terminate more superiorly, to the cuneus.
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The target was a shaded region of the top right-hand side corner; however, similar targets were presented in the unattended bottom half of the object in the attended visual field and in the top and bottom halves of the object in the unattended visual field. As expected, when comparing targets in the attended visual field to targets in the unattended visual field, it was found that the amplitude of the N1 was greater for attended (vs. unattended) objects. Additionally, although the amplitude of the N1 was greatest for targets in the attended visual field and the attended part of object, the amplitude of the N1 for targets in the unattended portion of the attended object was larger than the amplitude of the N1 for targets at an equivalent distance from the locus of attention but on an unattended object.
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Several other stars in the same visual field have been catalogued as companions but are physically unrelated.
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Even a small scotoma that happens to affect central or macular vision will produce a severe visual disability, whereas a large scotoma in the more peripheral part of a visual field may go unnoticed by the bearer because of the normal reduced optical resolution in the peripheral visual field.
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In 1997, the trials were temporarily suspended because it was linked to peripheral visual field defects in humans.
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Nevertheless, evidence for the efficacy of cost-effective interventions aimed at these visual field defects is still inconsistent.
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Similarly, another patient with unilateral lesion of area V1 could avoid obstacles placed in his blind field when he reached toward a target that was visible in his intact visual field. Even though he avoided the obstacles, he never reported seeing them. A study reported in 2008 asked patient GY to misstate where in his visual field a distinctive stimulus was presented. If the stimulus was in the upper part of his visual field, he was to say it was in the lower part, and vice versa.
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The flocculus appears to be included a VOR pathway that aids in the adaptation to a repeated shift in the visual field. A shift in the visual field affects an individuals spatial recognition. The leading research would suggest that flocculus aids in the synchronization of eye and motor functions after a visual shift occurs in order for the visual field and the motor skills to function together. If this shift is repeated the flocculus essentially trains the brain to fully readjust to this repeated stimuli.
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A visual field test is an eye examination that can detect dysfunction in central and peripheral vision which may be caused by various medical conditions such as glaucoma, stroke, pituitary disease, brain tumours or other neurological deficits. Visual field testing can be performed clinically by keeping the subject's gaze fixed while presenting objects at various places within their visual field. Simple manual equipment can be used such as in the tangent screen test or the Amsler grid. When dedicated machinery is used it is called a perimeter.
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E. clarus possesses compound eyes that lack pigment in the iris region. Each ommatidia, or single optical unit, has its own unique visual field that spans about 2°. The small visual field can be due to crystalline tracts in the eye that restrict the light to reach the retina only through this path.
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He lost his visual field beyond a 30-degree eccentricity and could not identify visual objects by their proper names.
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As stimuli move across the toad's visual field, information is sent to the optic tectum in the toad's midbrain. The optic tectum exists as an ordered localization system, in the form of a topographical map. Each point on the map corresponds to a particular region of the toad's retina and thus its entire visual field.
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By the 11th day, double simultaneous stimulation showed rare mistakes being made on the right side of his visual field as well as unawareness of the right side of his body. These symptoms caused a diagnosis of Amorphosynthesis. Although the patient made rare mistakes on the right side of his visual field, he also showed improvement when playing chess by correctly using his pieces, making more passive moves and blunts on the right side on the chessboard. Double simultaneous testing revealed a fully intact right visual field as well as movement.
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This in turn results in the complete negligence of the left visual hemifield. With the use of prism adaptation, their visual-attention frame is realigned so that some of the neglected left visual field comes into attentional focus. The use of right- deviating prisms shifts the patient's entire visual field to the right and realigns the left visual field into attentional focus. This spatial realignment has proven to persist long after prism exposure and ameliorate unilateral neglect symptoms by allowing the patient to be aware of the previously neglected side of space.
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For example, in a Filtering Paradigm (see description above), participants were instructed to identify targets based on either color or motion. In some cases, participants were told to attend to one side of the visual field, while in other cases participants' attention was not focused on one side of the visual field. It was found that the amplitude of the N1 was greater for targets of the correct color and motion when participants were instructed to attend to one side of the visual field versus when they were not instructed to do so.
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Unidirectional visual trails or illusory symptoms confined to part of a visual field suggest cortical pathology and necessitate further work-up.
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He was able to misstate, as requested, in his left visual field (with normal conscious vision); but he tended to fail in the task—to state the location correctly—when the stimulus was in his blindsight (right) visual field. This failure rate worsened when the stimulus was clearer, indicating that failure was not simply due to unreliability of blindsight.
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Henning Rønne specialized in the pathological anatomy of the eye, and is remembered for campimetric studies involving the eyes' visual field. He also performed investigations involving the primary visual centres of the midbrain. His name is lent to the eponymous "Rønne nasal step", defined as a nasal visual field defect that is considered a pathognomonic sign of glaucoma.
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A scar in the central visual field would be more debilitating. Generally, a limited visual field defect, which will be barely noticeable, is all that is likely to occur. When thermal radiation strikes an object, part will be reflected, part transmitted, and the rest absorbed. The fraction that is absorbed depends on the nature and color of the material.
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This effect describes the instability of one's visual field of vision, and becomes the basis for Barth's next series of works Grounds.
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2004;45:729-738 Perhaps the most important finding is that a two-dimensional representation of the visual field is sufficient for most purposes.
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The dorsal stream (green) and ventral stream (purple) are both actively involved in visual memory. Both pathways originate in the visual cortex There is a visual cortex in each hemisphere of the brain, much of which is located in the Occipital lobe. The left hemisphere visual cortex receives signals mainly from the right visual field and the right visual cortex mainly from the left visual field, although each cortex receives a considerable amount of information from the ipsilateral visual field as well. The visual cortex also receives information from subcortical regions, such as the lateral geniculate body, located in the thalamus.
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This occurs in 24% of cases. Visual field loss in bitemporal hemianopsia: compression of the optic chiasm leads to a characteristic pattern of vision loss affecting the outer halves of each eye. Pressure on the part of the optic nerve known as the chiasm, which is located above the gland, leads to loss of vision on the outer side of the visual field on both sides, as this corresponds to areas on the retinas supplied by these parts of the optic nerve; it is encountered in 75% of cases. Visual acuity is reduced in half, and over 60% have a visual field defect.
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Visual hallucinations due to focal seizures differ depending on the region of the brain where the seizure occurs. For example, visual hallucinations during occipital lobe seizures are typically visions of brightly colored, geometric shapes that may move across the visual field, multiply, or form concentric rings and generally persist from a few seconds to a few minutes. They are usually unilateral and localized to one part of the visual field on the contralateral side of the seizure focus, typically the temporal field. However, unilateral visions moving horizontally across the visual field begin on the contralateral side and move toward the ipsilateral side.
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In many locations within the brain, adjacent neurons have receptive fields that include slightly different, but overlapping portions of the visual field. The position of the center of these receptive fields forms an orderly sampling mosaic that covers a portion of the visual field. Because of this orderly arrangement, which emerges from the spatial specificity of connections between neurons in different parts of the visual system, cells in each structure can be seen as contributing to a map of the visual field (also called a retinotopic map, or a visuotopic map). Retinotopic maps are a particular case of topographic organization.
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It arises from the compression of the optic nerve by the tumor. The specific area of the visual pathway at which compression by these tumours occurs is at the optic chiasma. The anatomy of this structure causes pressure on it to produce a defect in the temporal visual field on both sides, a condition called bitemporal hemianopsia. If originating superior to the optic chiasm, more commonly in a craniopharyngioma of the pituitary stalk, the visual field defect will first appear as bitemporal inferior quadrantanopia, if originating inferior to the optic chiasm the visual field defect will first appear as bitemporal superior quadrantanopia.
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Psychology Science, 8, 368-373. There are two types of saccadic suppression, with the first concerning the detection of light spot flashes during saccades. The lower the spatial frequency, meaning fewer objects in the visual field of the light flashes, the stronger the saccadic suppression. With fewer items in the visual field it is easier for saccadic suppression to occur.
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50 lenses are then used, there is usually a dramatic improvement as observed by patient and parent. Abnormal results on color vision or visual field testing is not uncommon. Visual field often presents as constricted 'tubular' at multiple test distances. The poor visual performance is understood as distress, and treatments are usually to provide the patient with low powered reading glasses.
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The lateral geniculate nucleus (LGN) is the nucleus in the thalamus that receives visual information from the retina and sends it to the visual cortex via optic radiations. A lesion of this nucleus produces moderately to completely congruent visual field defects. Isolated lesions of the lateral geniculate nucleus are rare, it may be diagnosed by distinctive patterns of visual field loss.
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The computer then automatically maps and calculates the patient's visual field.Siverstone, DE, Hirsch, J: Automated Visual Field Testing. Appelton-Century Croft. Norwalk, CT. 1986.
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Binasal occlusion is a method of partial covering (occlusion) of the visual field of the two eyes in which the sector of the visual field that is adjacent to the nose (the nasal visual field) is occluded for each eye. It is a well- known procedure in vision therapy. By blocking parts of the image that would be seen by both eyes, binocular occlusion reduces the visual stress that would be related diplopia and binocular rivalry. In contrast to an eye patch that occludes the whole visual field of one eye, binocular occlusion allows some degree of binocular vision; more particularly, it emphasizes the role of binocular functioning in peripheral vision: objects that are located to the right can only be fixated by the right eye, and those located to the left only by the left eye.
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For example, in the second visual area (V2), the map is divided along an imaginary horizontal line across the visual field, in such a way that the parts of the retina that respond to the upper half of the visual field are represented in cortical tissue that is separated from those parts that respond the lower half of the visual field. Even more complex maps exist in the third and fourth visual areas V3 and V4, and in the dorsomedial area (V6). In general, these complex maps are referred to as second-order representations of the visual field, as opposed to first- order (continuous) representations such as V1. Additional retinotopic regions include ventral occipital (VO-1, VO-2), lateral occipital (LO-1, LO-2), dorsal occipital (V3A, V3B), and posterior parietal cortex (IPS0, IPS1, IPS2, IPS3, IPS4).
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Confrontation visual field testing is a simple and quick visual field assessing method. A confrontational field test requires little or no special equipment and can be performed in any room, which is well illuminated. Patient sitting straight in front of the examiner, is asked look directly at the examiner's eye during the test. The target eye should be the one directly across from the patient's eye.
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Tumours and other compressive lesions could often present with visual impairment and/or visual field defects. Careful clinical assessment could aid in accurate diagnosis of the cause of the visual field defect and loss of vision. Compressive lesions of the visual pathway, especially lesions affecting optic nerve require a multi-disciplinary approach involving neurosurgeon, physician as well as the ophthalmologist. Treatment is given according to the cause.
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Lamb In sheep breeds lacking facial wool, the visual field is wide. In 10 sheep (Cambridge, Lleyn and Welsh Mountain breeds, which lack facial wool), the visual field ranged from 298° to 325°, averaging 313.1°, with binocular overlap ranging from 44.5° to 74°, averaging 61.7°.Piggins, D. and C. J. C. Phillips. 1996. The eye of the domesticated sheep and its implications for vision.
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Kuzhuppilly N, Patil S, Dev S, Deo A. Reliability of Visual Field Index in Staging Glaucomatous Visual Field Damage. Journal of Clinical & Diagnostic Research. 2018 Jun 1;12(6): NC05-NC08 The shaded pattern of vision loss provided on the Pattern Deviation plot allows for diagnosis of the type of vision loss present. This contributes to other clinical findings in the diagnosis of certain conditions.
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Dermatochalasis is caused by a loss of elasticity in the connective tissue supporting the structure of the front portion of the eyelid. Normally, in Caucasians, the orbicularis muscle and overlying skin form a crease near the tarsal border. In dermatochalasis, the excess tissues hangs down, over the front edge of the eyelid. The excess tissue can sometimes obstruct the visual field, especially the superior visual field.
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Techniques used to perform this test include the confrontation visual field examination (Donders' test). The examiner will ask the patient to cover one eye and stare at the examiner. Ideally, when the patient covers their right eye, the examiner covers their left eye, and vice versa. The examiner will then move his hand out of the patient's visual field and then bring it back in.
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The extrastriate areas consist of visual areas 2, 3, 4, and 5 (also known as V2, V3, V4, and V5, or Brodmann area 18 and all Brodmann area 19). Both hemispheres of the brain include a visual cortex; the visual cortex in the left hemisphere receives signals from the right visual field, and the visual cortex in the right hemisphere receives signals from the left visual field.
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The divided visual field technique in laterality and interhemispheric integration. In K. Hughdahl (Ed.), Experimental Methods in Neuropsychology (pp. 47-63). New York: Kluwer.Bourne, V.J. (2006).
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Therefore, its possible for the cilio retinal artery itself to occlude causing significant visual loss in the perfused macula region (surrounding visual field will remain intact).
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The condition is diagnosed using ocular tonometry and glaucoma evaluation. Increased IOP without glaucomatous changes (in optic disc or visual field) is considered as ocular hypertension.
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Sloan also contributed greatly to the creation of the First International Standard for Visual Field Testing committee, where she represented the American optics and visual physiology committee.
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The earliest signs of toxicity include bilateral paracentral visual field changes (best detected with a red test object) and a subtle granular depigmentation of the paracentral RPE.
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Strasburger, Hans; Pöppel, Ernst (2002). Visual Field. In G. Adelman & B.H. Smith (Eds): Encyclopedia of Neuroscience; 3rd edition, on CD-ROM. Elsevier Science B.V., Amsterdam, New York.
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For the participant to be able to do this, he/she has to ignore cues in the visual field. If the participant adjusts the rod so that it is leaning in the direction of the tilted frame, then that person is said to be dependent on the visual field. This person will be categorized as field-dependent. On the other side there will be people who are field-independent.
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Daniel Voyer proposed some criticism for the word frequency effect in 2003 after experiments on laterality effects in lexical decisions. His experiments demonstrated two findings: :(1) Word frequency effect was only significant for the left visual field presentation :(2) In a case-altered condition, the word frequency effect meaningful for right visual field presentations. Voyer further posits that hemispheric asymmetries may play a role in the word frequency effect.
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306x306px Humphrey field analyser (HFA), is a tool for measuring the human visual field, it is used by optometrists, orthoptists and ophthalmologists, particularly for detecting monocular visual field. The results of the Analyser identify the type of vision defect. Therefore, it provides information regarding the location of any disease processes or lesion(s) throughout the visual pathway. This guides and contributes to the diagnosis of the condition affecting the patient's vision.
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When targets in the attended visual field are compared to targets in the unattended visual field, the unattended targets are found to elicit a smaller N1 than the attended targets, suggesting that attention acts as a sensory gain mechanism that enhances perception of attended (vs. unattended) stimuli.Naatanen, R. & Michie, P.T. Early selective-attention effects of the evoked potential: A critical review and reinterpretation. (1979). Biological Psychology 8: 81-136.
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Hallucinatory palinopsia describes afterimages or scenes that are formed, long-lasting, high resolution, and isochromatic. The palinoptic images are not typically reliant on environmental parameters and often present with homonymous visual field deficits. Hallucinatory palinopsia occurs unpredictably and the persistent images can appear anywhere in the visual field, regardless of the location of the original stimulus. A patient will often have only a few episodes of hallucinatory palinopsia.
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Some reported that the LF travel across the visual field, moving from the periphery of the visual field to where the person is fixating, while a couple of others reported motion in the opposite direction. Terms that have been used to describe the directions are "sideways", "diagonal", "in-out" and "random". In Fuglesang et al. (2006), it was pointed out that there were no reports of vertical motion.
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The optic nerve, also known as cranial nerve II, extends from the optic disc to the optic chiasma. Lesions in optic nerve causes visual field defects and blindness.
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It is often contrasted with monophonic, or "mono" sound, where audio is in the form of one channel, often centered in the sound field (analogous to a visual field).
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Stimuli presented in the right half of the visual field will elicit a negativity over the leftward occipital and parietal channels. While the polarity is consistent across presentations of visual stimuli in different visual fields, the P1s scalp topographic maps do change in that the positivity is elicited contralaterally to the visual field in which a stimulus is presented although not to the extent shown in the C1 component (Mangun et al., 1993).
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Identification of glaucoma-related visual field abnormality with the screening protocol of frequency doubling technology. American Journal of Ophthalmology, 125, 819-829Burnstein, Y., Ellish, N.J., Magbalon, M. & Higginbotham, E.J. (2000). Comparison of frequency doubling perimetry with humphrey visual field analysis in a glaucoma practice. American Journal of Ophthalmology, 129, 328-333 A more recent study's results argue against the hypothesis that spatially nonlinear retinal ganglion cells are the physiological substrate of the frequency-doubling illusion.
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Glaucoma is a type of blindness that begins at the edge of the visual field and progresses inward. It may result in tunnel vision. This typically involves the outer layers of the optic nerve, sometimes as a result of buildup of fluid and excessive pressure in the eye. Scotoma is a type of blindness that produces a small blind spot in the visual field typically caused by injury in the primary visual cortex.
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Prolonged indistinct afterimages are unformed and occur at the same location in the visual field as the original stimulus. Stimulus intensity, contrast, and fixation length affects the generation and severity of these perseverated images. For example, after seeing a bright light such as a car headlight or a camera flash, a persistent afterimage remains in the visual field for several minutes. Patients often report photophobia, which can restrict their ability to perform outdoor activity.
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A patient commonly complains of the perseverated fingers of an examiner. These afterimages often occur in visual field deficits but may occur anywhere in the visual field, regardless of the location of the original stimulus. The generation of the afterimages is not affected by external conditions such as the length of fixation, stimulus intensity, contrast, or motion. The palinoptic image can appear immediately after seeing the original image or may be delayed in time.
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Therefore, on the scale of connectedness and complexity, CNNs are on the lower extreme. Convolutional networks were inspired by biological processes in that the connectivity pattern between neurons resembles the organization of the animal visual cortex. Individual cortical neurons respond to stimuli only in a restricted region of the visual field known as the receptive field. The receptive fields of different neurons partially overlap such that they cover the entire visual field.
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Visual field testing is recommended as soon as possible after diagnosis, as it quantifies the severity of any optic nerve involvement, and may be required to decide on surgical treatment.
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If a lesion only exists in one optic radiation, the consequence is called quadrantanopia, which implies that only the respective superior or inferior quadrant of the visual field is affected.
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Volume 29. Issue 2 (2010): 167-182. Digital. When an element in a visual field disconnects from the ‘whole’ created by the brain's perceptual organization, it “stands out” to the viewer.
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Diagram of lateralized visual pathways of the human brain The Divided Visual Field Paradigm is an experimental technique that involves measuring task performance when visual stimuli are presented on the left or right visual hemifields. If a visual stimulus appears in the left visual field (LVF), the visual information is initially projected to the right cerebral hemisphere (RH), and conversely, if a visual stimulus appears in the right visual field (RVF), the visual information is initially received by the left cerebral hemisphere (LH). In this way, if a cerebral hemisphere has functional advantages with some aspect of a particular task, an experimenter might observe improvements in task performance when the visual information is presented on the contralateral visual field.Banich, M.T. (2003).
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In 1978, Michael Gazzaniga and Joseph DeLoux discovered a unique phenomenon among split-brain patients who were asked to perform a simultaneous concept task. The patient was shown 2 pictures: of a house in the winter time and of a chicken's claw. The pictures were positioned so they would exclusively be seen in only one visual field of the brain (the winter house was positioned so it would only be seen in the patient's left visual field (LVF), which corresponds to the brain's right hemisphere, and the chicken's claw was placed so it would only be seen in the patient's right visual field (RVF), which corresponds to the brain's left hemisphere). A series of pictures was placed in front of the patients.
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Patients with optic disc drusen should be monitored periodically via ophthalmoscopy, Snellen acuity, contrast sensitivity, color vision, intraocular pressure and threshold visual fields. For those with visual field defects optical coherence tomography has been recommended for follow up of nerve fiber layer thickness. Associated conditions such as angioid streaks and retinitis pigmentosa should be screened for. Both the severity of optic disc drusen and the degree of intraocular pressure elevation have been associated with visual field loss.
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Architecture of the optic chiasm and the mechanisms that sculpt its development. Physiological Reviews, 81(4), 1393-1414. Stimuli presented on the right visual field (RVF) will ultimately be processed first by the left hemisphere's (LH) occipital cortex, while stimuli presented on the left visual field (LVF) will be processed first by the right hemisphere's (RH) occipital cortex. Because lateralized visual information is initially segregated between the two cerebral hemispheres, any differences in task performance (e.g.
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This is inconsistent with discrete frames covering the entire visual scene. Kline, Holcombe, and Eagleman (2006) also showed that reversed rotation of a radial grating in one part of the visual field was independent of superimposed orthogonal motion in the same part of the visual field. The orthogonal motion was of a circular grating contracting so as to have the same temporal frequency as the radial grating. This is inconsistent with discrete frames covering local parts of visual scene.
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During prism adaptation, an individual wears special prismatic goggles that are made of prism wedges that displace the visual field laterally or vertically. In most cases the visual field is shifted laterally either in the rightward or leftward direction. While wearing the goggles, the individual engages in a perceptual motor task such as pointing to a visual target directly in front of them. A prism adaptation session includes three components: the pre-test, prism exposure, and the post-test.
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It is debated in research on visual spatial attention whether it is possible to split attention across different areas in the visual field. The ‘spotlight’ and ‘zoom-lens’ accounts postulate that attention uses a single unitary focus. Therefore, spatial attention can only be allocated to adjacent areas in the visual field and consequently cannot be split. This was supported by an experiment that altered the spatial cueing paradigm by using two cues, a primary and a secondary cue.
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Patients with macular splitting fare much more poorly on such tasks, particularly if they lose vision in their right visual field. This is because the right visual field projects to the left hemisphere, where most people are language dominant. People with macular sparing may experience difficulty with moving around, especially in crowds, because they might unintentionally bump into people or objects in their periphery where they cannot see.Zhang, X., Kedar, S., Lynn, M., Newman, N., & Biousse, V. (2006).
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Effects of spatial cuing on luminance detectability: Psychophysical and electrophysiological evidence for early selection. Journal of Experimental Psychology: Human Perception and Performance, 20, 887-904. Additionally, the amplitude of the N1 is believed to represent a sensory gain control mechanism because focusing attention on one area of the visual field serves to increase the amplitude of the N1 to relevant perceptual information presented in that field (vs. the other visual field), and thus facilitates further perceptual processing of stimuli.
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Homonymous hemianopia is a type of blindness that destroys one entire side of the visual field typically caused by injury in the primary visual cortex. Quadrantanopia is a type of blindness that destroys only a part of the visual field typically caused by partial injury in the primary visual cortex. This is very similar to homonymous hemianopia, but to a lesser degree. Prosopagnosia, or face blindness, is a brain disorder that produces an inability to recognize faces.
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The degree of vision loss can extend to total blindness, but a loss beyond 20/400 is rare, except in the case of methanol ingestion. Peripheral vision is usually spared since the pattern of loss typically involves a central or cecocentral scotoma, a visual field defect at or surrounding the point of fixation. This pattern can be revealed via visual field testing. Upon examination, the pupils usually demonstrate a normal response to light and near stimulation.
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The discovery of visual field maps in humans can be traced to neurological cases, arising from war injuries, described and analyzed independently by Tatsuji Inouye (a Japanese ophthalmologist) and Gordon Holmes (a British neurologist). They observed correlations between the position of the entry wound and visual field loss (see Fishman, 1997Ronald S. Fishman (1997). Gordon Holmes, the cortical retina, and the wounds of war. The seventh Charles B. Snyder Lecture Documenta Ophthalmologica 93: 9-28, 1997.
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By comparing the test results of both GY and the monkeys, the researchers concluded that similar patterns of responses to stimuli in the "blind" visual field can be found in both species.
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A 2005 study examined 92 case studies since 1970 in which cerebral lesions affected color vision. The severity and size of the visual field affected in cerebral achromatopsiacs vary from patient to patient.
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Receptive fields partially overlap, over-covering the entire visual field. Unit response can be approximated mathematically by a convolution operation. CNNs are suitable for processing visual and other two- dimensional data.LeCun et al.
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The H1 neuron is responsible for detecting horizontal motion across the entire visual field of the fly, allowing the fly to generate and guide stabilizing motor corrections mid-flight with respect to yaw.
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Suppression of an eye is a subconscious adaptation by a person's brain to eliminate the symptoms of disorders of binocular vision such as strabismus, convergence insufficiency and aniseikonia. The brain can eliminate double vision by ignoring all or part of the image of one of the eyes. The area of a person's visual field that is suppressed is called the suppression scotoma (with a scotoma meaning, more generally, an area of partial alteration in the visual field). Suppression can lead to amblyopia.
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Meridian (plural: "meridians") is used in perimetry and in specifying visual fields. According to IPS Perimetry Standards 1978 (2002): "Perimetry is the measurement of [an observer's] visual functions ... at topographically defined loci in the visual field. The visual field is that portion of the external environment of the observer [in which when he or she is] steadily fixating ...[he or she] can detect visual stimuli." In perimetry, the observer's eye is considered to be at the centre of an imaginary sphere.
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Visual processing in the brain goes through a series of stages. Destruction of the primary visual cortex leads to blindness in the part of the visual field that corresponds to the damaged cortical representation. The area of blindness – known as a scotoma – is in the visual field opposite the damaged hemisphere and can vary from a small area up to the entire hemifield. Visual processing occurs in the brain in a hierarchical series of stages (with much crosstalk and feedback between areas).
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A variant of this paradigm is the filter paradigm. In this paradigm participants are asked to attend to a certain part of the visual field and to not pay attention to or "filter out" the rest of the visual field. Blocks of stimuli are presented one at a time in both attended and unattended space. Participants are to look for a target that differs from the rest of the stimuli on some number of dimensions such as size, length, luminance, etc.
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Hemianopsia, or hemianopia, is a visual field loss on the left or right side of the vertical midline. It can affect one eye but usually affects both eyes. Homonymous hemianopsia (or homonymous hemianopia) is hemianopic visual field loss on the same side of both eyes. Homonymous hemianopsia occurs because the right half of the brain has visual pathways for the left hemifield of both eyes, and the left half of the brain has visual pathways for the right hemifield of both eyes.
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In fact, researchers have found a similar memory effect for words that were presented visually. They found a repetition effect for words that had been studied in the left visual field, (encoded in the right hemisphere), but not in the right visual field. The P2 amplitude was bigger for words that had been seen before. This indicates that P2 amplitude is modulated by aspects of recognition and that there is a hemispheric difference (which may be important for language processing, see below).
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Both the right and left hemispheres generate an N1, but the laterality of the N1 depends on whether a stimulus is presented centrally, laterally, or bilaterally. When a stimulus is presented centrally, the N1 is bilateral. When presented laterally, the N1 is larger, earlier, and contralateral to the visual field of the stimulus. When two visual stimuli are presented, one in each visual field, the N1 is bilateral. In the latter case, the N1's asymmetrical skewedness is modulated by attention.
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There is no direct conscious awareness of visual scotomas. They are simply regions of reduced information within the visual field. Rather than recognizing an incomplete image, patients with scotomas report that things "disappear" on them. The presence of the blind spot scotoma can be demonstrated subjectively by covering one eye, carefully holding fixation with the open eye, and placing an object (such as one's thumb) in the lateral and horizontal visual field, about 15 degrees from fixation (see the blind spot article).
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Revonsuo explains a procedure that was similar in nature to the Sperry–Gazzaniga design. Split-brain patients are shown a picture with two objects: a flower and a rabbit. The flower is exclusively shown in the right visual field, which is interpreted by the left hemisphere and the rabbit is exclusively shown in the left visual field, which is interpreted by the right hemisphere. The left brain is seeing the flower as the right brain is simultaneously viewing the rabbit.
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Most cases of polyopia are accompanied by another neurological condition. Polyopia is often accompanied by visual field defects (such as the presence of a scotoma) or transient visual hallucinations. Polyopic images often form in the direction and position of such visual field defects. Current research shows that when stimuli are close to the patient’s scotoma, the latency of polyopic images is much shorter than if the stimuli was far from the scotoma, and there is a higher probability that polyopic images will result.
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General indications for pituitary surgery include patient drug intolerance, tumors resistant to medical therapy, patients who have persistent visual field defects in spite of medical treatment, and patients with large cystic or hemorrhagic tumors.
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The Men's 100 metres, T13 was held on January 26 T12 = may recognise the shape of a hand, have a visual acuity of 2/60 and/or visual field of less than 5 degrees.
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Ancillary testing is not usually necessary to make the diagnosis. Fluorescein angiography reveals an abrupt diminution in dye at the site of the obstruction. Visual field testing can confirm the extent of visual loss.
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He may got the idea of the grid from Edmund Landolt, who used a similar small card with a grid pattern to be kept in the center of the visual field testing instrument perimeter.
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Signs of the tumor resulting from increased intracranial pressure are present in 91% of patients, with vomiting, homonymous visual field defects and headache being the most common symptoms. Other symptoms are ear ringing and dizziness.
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Chimpanzee infants are sensitive to faces which are gazing at them, but chimpanzees less than three to four years old only look within their visual field when using the experimenter's head turn as their cue.
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It was also found that the longer an infant focuses on an object may be due to detected discontinuities in their visual field, or the flow of events, with which the infant has become familiar.
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Responses to this treatment can vary and are impacted if the patient is diagnosed with any type of cancer. Patients who respond positively show improvement in the clarity of their vision and their visual field.
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The types of vision loss and associated conditions are not described in the extent of this article, however Figure 5 provides typical examples of visual field loss seen. Refer to #See also for more information.
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Ever since this experiment, the difference between the P1 amplitude when the participant is attending in the correct and incorrect visual field (or the P1 effect) has been extensively studied as part of selective attention.
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In a 1995 experiment, researchers attempted to show that monkeys with lesions in or even wholly removed striate cortexes also experienced blindsight. To study this, they had the monkeys complete tasks similar to those commonly used on human subjects. The monkeys were placed in front of a monitor and taught to indicate whether a stationary object or nothing was present in their visual field when a tone was played. Then the monkeys performed the same task except the stationary objects were presented outside of their visual field.
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A significant difference between RVF/LH and LVF/RH task performance using the divided visual field paradigm does provide evidence of a functional asymmetry between the two cerebral hemispheres. However, as described by Ivry and Robertson (1998), there are limitations to the types of inferences that can be made from this technique: > These [divided visual field] methods have their limitations. A critical > assumption has been that differences in performance with lateralized stimuli > nearly always reflect functional differences between the two hemispheres. > This is an extremely strong assumption.
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Homonymous hemianopsia secondary to posterior cerebral artery occlusion - may result in syndromes of memory impairment, opposite visual field loss (homonymous hemianopsia), and sometimes hemisensory deficits. The PCA supplies the occipital lobe and the medial portion of the temporal lobe. Infarction of occipital cortex typically causes macular sparing hemianopias due to dual blood supply from both posterior cerebral artery and middle cerebral artery. Occlusion of the calcarine artery that results in infarction of the superior part of the occipital lobe causes a lower peripheral visual field defect.
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Prisms or "field expanders" that bend light have been prescribed for decades in patients with hemianopsia. Higher power Fresnel ("stick-on") prisms are commonly employed because they are thin and lightweight, and can be cut and placed in different positions on a spectacle lens. Peripheral prism spectacles expand the visual field of patients with hemifield visual defects and have the potential to improve visual function and mobility.Bowers AR, Keeney K, Peli E. Community-based trial of a peripheral prism visual field expansion device for hemianopia.
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Damage at the optic chiasm itself typically causes loss of vision laterally in both visual fields or bitemporal hemianopsia (see image to the right). Such damage may occur with large pituitary tumors, such as pituitary adenoma. Finally, damage to the optic tract, which is posterior to, or behind the chiasm, causes loss of the entire visual field from the side opposite the damage, e.g. if the left optic tract were cut, there would be a loss of vision from the entire right visual field.
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The exam may be performed by a technician in one of several ways. The test may be performed by a technician directly, with the assistance of a machine, or completely by an automated machine. Machine based tests aid diagnostics by allowing a detailed printout of the patient's visual field. Other names for this test may include perimetry, Tangent screen exam, Automated perimetry exam, Goldmann visual field exam, or brand names such as Humphrey Field Analyzer, Octopus Perimeter, Optopol PTS perimeter, Oculus Easyfield perimeter, Olleyes VisuALL, etc.
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Objects were then represented in the central visual field at either the same orientation or a different orientation than the original image. Then participants were asked to name if the same or different depth- orientation views of these objects presented. The same procedure was then executed when presenting the images to the left or right visual field. Viewpoint-dependent priming was observed when test views were presented directly to the right hemisphere, but not when test views were presented directly to the left hemisphere.
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An unhealthy weight can further complicate mobility. Patients with spastic hemiplegia are a high risk for experiencing seizures. Oromotor dysfunction puts patients at risk for aspiration pneumonia. Visual field deficits can cause impaired two-point discrimination.
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The Men's 200 metres, T12 was held on January 27 and 29 T12 = may recognise the shape of a hand, have a visual acuity of 2/60 and/or visual field of less than 5 degrees.
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The Men's discus throw, F12 was held on January 28 F12 = visual impairment: may recognise the shape of a hand, have a visual acuity of 2/60 and/or visual field of less than 5 degrees.
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Due to the independence of the stimulus sequences, the responses for each visual field location can be extracted using mathematical algorithms. Mutifocal techniques, in particular the multifocal ERG, are used in the diagnosis of ophthalmological diseases.
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Thus, the visual and mechanosensory (halteres) systems work together to stabilize the visual field of the animal: first, by quickly responding to fast changes (halteres), and second, by maintaining that response until it is corrected (vision).
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Meridians correspond to sections of great circles passing through the centre of the fovea. In an analogy to Meridian (geography), in which meridians are lines of longitude, the North pole might correspond to the fovea, Greenwich would correspond to a retinal location about 39 degrees to the left of the fovea (because the retinal image is inverted, this corresponds to a location in the visual field to the observer's right), and the South pole would correspond to the centre of the pupil. The meridian of the visual field has been found to influence the folding of the cerebral cortex. In both the V1 and V2 areas of macaques and humans the vertical meridian of their visual field tends to be represented on the cerebral cortex's convex gyri folds whereas the horizontal meridian is tends to be represented in their concave sulci folds.
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Braddick using fMRI has suggested that area V3/V3A may play a role in the processing of global motion Other studies prefer to consider dorsal V3 as part of a larger area, named the dorsomedial area (DM), which contains a representation of the entire visual field. Neurons in area DM respond to coherent motion of large patterns covering extensive portions of the visual field (Lui and collaborators, 2006). Ventral V3 (VP), has much weaker connections from the primary visual area, and stronger connections with the inferior temporal cortex. While earlier studies proposed that VP contained a representation of only the upper part of the visual field (above the point of fixation), more recent work indicates that this area is more extensive than previously appreciated, and like other visual areas it may contain a complete visual representation.
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Retinal detachment should be considered if there were preceding flashes or floaters, or if there is a new visual field defect in one eye. If treated early enough, retinal tear and detachment can have a good outcome.
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Along with the insidious development of ptosis, eye movements eventually become limited causing a person to rely more on turning the head side to side or up and down to view objects in the peripheral visual field.
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Later in 1985, Eva Wong and Weisstein indicated that the depth segregation (the perception of flickering regions lies behind the non- flickering regions in visual field) is caused by a visual channel response to higher temporal frequency.
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The optic chiasm is formed by the union of the two optic nerves. The nasal fibers of each optic nerve decussate (cross) across the chiasm to the contralateral side while the temporal fibers course posteriorly to form the optic tract on the ipsilateral side. This arrangement allows the left half of the visual field to end up on the right side of the brain and the right half of the visual field to locate to the left side. The optic nerves consist of the axons from the retinal ganglion of each eye.
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That's why head movements in birds play bigger role than eye movements. Two eyes usually move independently, and in some species they can move coordinatedly in opposite directions. Birds with eyes on the sides of their heads have a wide visual field, useful for detecting predators, while those with eyes on the front of their heads, such as owls, have binocular vision and can estimate distances when hunting. The American woodcock probably has the largest visual field of any bird, 360° in the horizontal plane, and 180° in the vertical plane.
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The decision on whether to surgically decompress the pituitary gland is complex and mainly dependent on the severity of visual loss and visual field defects. If visual acuity is severely reduced, there are large or worsening visual field defects, or the level of consciousness falls consistently, professional guidelines recommend that surgery is performed. Most commonly, operations on the pituitary gland are performed through transsphenoidal surgery. In this procedure, surgical instruments are passed through the nose towards the sphenoid bone, which is opened to give access to the cavity that contains the pituitary gland.
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Trends in Neurosciences 17 (10): 402–404. In performing the initial experiments, Gazzaniga and his colleagues observed what happened when the left and right hemispheres in the split brains of patients were unable to communicate with each other. In these experiments when patients were shown an image within the right visual field (which maps to the left brain hemisphere), an explanation of what was seen could be provided. However, when the image was only presented to the left visual field (which maps to the right brain hemisphere) the patients stated that they didn't see anything.
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For example, the horizontal meridian runs from the observer's left, through the fixation point, and to the observer's right. The vertical meridian runs from above the observer's line of sight, through the fixation point, and to below the observer's line of sight. Another way of thinking of the maximum visual field is to think of all of the retina that can be reached by light from the external environment. The visual field in this case is all of the external environment that can project light onto the retina.
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In visual allochiria, objects situated on one side of the visual field are perceived in the contralateral visual field. In one of the two cases ever recorded, the visual impression received by the right open eye was regularly referred to the left eye, and the patient maintained that she perceived the impression with the left eye that in fact was shut. In the other case, a colored object held in front of the left eye was recognized and the patient maintained that she saw the color with the right eye.
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Differences in brain activation in the left and right hemisphere seem to be indicative of insight versus non-insight solutions. Using RAT’s that were either presented to the left or right visual field, it was shown that participants having solved the problem with insight were more likely to have been shown the RAT on the left visual field, indicating right hemisphere processing. This provides evidence that the right hemisphere plays a unique role in insight. fMRI and EEG scans of participants completing RAT's demonstrated unique brain activity corresponding to problems solved by insight.
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In 2003, vigabatrin was shown by Frisén and Malmgren to cause irreversible diffuse atrophy of the retinal nerve fiber layer in a retrospective study of 25 patients. This has the most effect on the outer area (as opposed to the macular, or central area) of the retina. Visual field defects had been reported as early as 1997 by Tom Eke and others, in the UK. Some authors, including Comaish et al. believe that visual field loss and electrophysiological changes may be demonstrable in up to 50% of Vigabatrin users.
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Retinal sensors convey stimuli through the optic tracts to the lateral geniculate bodies, where optic radiations continue to the visual cortex. Each visual cortex receives raw sensory information from the outside half of the retina on the same side of the head and from the inside half of the retina on the other side of the head. The cuneus (Brodmann's area 17) receives visual information from the contralateral superior retina representing the inferior visual field. The lingula receives information from the contralateral inferior retina representing the superior visual field.
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Stimuli that fill the entire visual field are more likely to cause seizures than those that appear in only a portion of the visual field. Stimuli perceived with both eyes are usually much more likely to cause seizures than stimuli seen with one eye only (which is why covering one eye may allow patients to avoid seizures when presented with visual challenges). Some patients are more sensitive with their eyes closed; others are more sensitive with their eyes open. Sensitivity is increased by alcohol consumption, sleep deprivation, illness, and other forms of stress.
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Single receptive field cells across the retina, LGN, and primary visual cortex are in a state of continuous neurotransmission. Impulse activity is the continuous state of regular and constant neurotransmission between neurons. Tests conducted by David H. Hubel and Torsten N. Wiesel (1968) utilized a single light dot presented within the visual field of a house cat to map out the location of a cell's receptive field within the cat's visual field. Orientation selectivity as it was first seen and measured in the cat's visual cortex via microelectrode analysis paired with visual stimulus.
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The VFI reflects retinal ganglion cell loss and function, as a percentage, with central points weighted more. It is expressed as a percentage of visual function; with 100% being a perfect age- adjusted visual field and 0% represents a perimetrically blind field. The pattern deviation probability plot (or total deviation probability plot when MD is worse than -20 dB) is used to identify abnormal points and age corrected sensitivity at each point is calculated using total deviation numerical map. VFI is a reliable index on which glaucomatous visual field severity staging can be based.
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Visual spatial attention is a form of visual attention that involves directing attention to a location in space. Similar to its temporal counterpart visual temporal attention, these attention modules have been widely implemented in video analytics in computer vision to provide enhanced performance and human interpretable explanation of deep learning models. Spatial attention allows humans to selectively process visual information through prioritization of an area within the visual field. A region of space within the visual field is selected for attention and the information within this region then receives further processing.
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Blocks of stimuli are presented one at a time and the participant must indicate (or at the very least look for) the target stimuli's presence. Before each block specific instructions are given as to what part of the visual field to attend to as well as any experiment specific instructions (e.g. Van Voorhis and Hillyard, 1977). The important comparison is between the P1 for targets that are presented in the space where a participant was attending versus targets that appear in parts of the visual field where the participants were not attending.
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The source of P1 component, as opposed to the C1 component, is not entirely known. Work by Mangun et al. (1993) with presenting bars in different sections of the visual field, some of which were presented in attended parts of the visual field and some were not, points to the neurological source of the P1 somewhere over the ventrolateral prestriate cortex or Brodmann's Area 18. To make this judgment, they used both current source density maps and structural MRI of the participants to localize the source of the P1.
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This type of perimetry is the most commonly used in clinical practice, and in research trials where loss of visual field must be measured. However, the sensitivity of white-on-white perimetry is low, and the variability is relatively high; as many as 25-50 percent of the photoreceptor cells may be lost before changes in visual field acuity are detected. This method is commonly used for early detection of blind spots. The patient sits in front of an (artificial) small concave dome in a small machine with a target in the center.
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It is postulated that by the "release phenomenon" MES is caused by hypersensitivity in the auditory cortex caused by sensory deprivation, secondary to their hearing loss. This "hole" in the hearing range is "plugged" by the brain confabulating a piece of information – in this case a piece of music. A similar occurrence is seen with strokes of the visual cortex where a visual field defect occurs and the brain confabulates a piece of visual data to fill the spot. This is described by sufferers as an image in the visual field.
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300px Peripheral vision of the human eye Field of view of the human eye Peripheral vision, or indirect vision, is vision as it occurs outside the point of fixation, i.e. away from the center of gaze. The vast majority of the area in the visual field is included in the notion of peripheral vision. "Far peripheral" vision refers to the area at the edges of the visual field, "mid- peripheral" vision refers to medium eccentricities, and "near-peripheral", sometimes referred to as "para-central" vision, exists adjacent to the center of gaze.
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In terms of visual acuity, "foveal vision" may be defined as vision using the part of the retina in which a visual acuity of at least 20/20 (6/6 metric or 0.0 LogMAR; internationally 1.0) is attained. This corresponds to using the foveal avascular zone (FAZ) with a diameter of 0.5 mm representing 1.5° of the visual field. Although often idealized as perfect circles, the central structures of the retina tend to be irregular ovals. Thus, foveal vision may also be defined as the central 1.5–2° of the visual field.
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Classical image of the shape and size of the visual fieldThe outer boundaries of peripheral vision correspond to the boundaries of the visual field as a whole. For a single eye, the extent of the visual field can be (roughly) defined in terms of four angles, each measured from the fixation point, i.e., the point at which one's gaze is directed. These angles, representing four cardinal directions, are 60° upwards, 60° nasally (towards the nose), 70–75° downwards, and 100–110° temporally (away from the nose and towards the temple).
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The rim of the retina contains a large concentration of cone cells. The retina extends farthest in the superior-nasal 45° quadrant (in the direction from the pupil to the bridge of the nose) with the greatest extent of the visual field in the opposite direction, the inferior temporal 45° quadrant (from the pupil of either eye towards the bottom of the nearest ear). Vision at this extreme part of the visual field is thought to be possibly concerned with threat detection, measuring optical flow, color constancy, or circadian rhythm.
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Photograph of United States Supreme Court building illustrating normal visual field, prior to onset of retinitis pigmentosa Photograph of the United States Supreme Court Building, modified to illustrate the effect of visual field loss, tunnel vision, in patients with Retinitis Pigmentosa. Retinitis pigmentosa is a progressive neurodegenerative disorder, which affects 1 in 3,000 individuals and affects between 50000 and 100000 people in the United States. Autosomal dominant RP accounts for approximately 15% of these cases. Autosomal dominant retinitis pigmentosa (ADRP) is a genetically heterogeneous group of inherited retinal degenerations that cause blindness in humans.
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2\. In primary sensory cortex, Hawkins predicts, for example, "we should find anticipatory cells in or near V1, at a precise location in the visual field (the scene)". It has been experimentally determined, for example, after mapping the angular position of some objects in the visual field, there will be a one-to-one correspondence of cells in the scene to the angular positions of those objects. Hawkins predicts that when the features of a visual scene are known in a memory, anticipatory cells should fire before the actual objects are seen in the scene.
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The Men's 200 metres, T13 was held on January 27 T13 = visual impairment: visual acuity ranges from 2/60 to 6/60 and/or has a visual field of more than 5 degrees and less than 20 degrees.
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Biased competition theory advocates the idea that each object in the visual field competes for cortical representation and cognitive processing. Desimone, R., & Duncan, J. (1995). Neural Mechanism of Selective Visual Attention. Annual Review of Neuroscience, 18, 193-222.
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In Kaprosuchus, the orbits (i.e., eye sockets) open laterally and are angled slightly forward rather than upward. The orbits turned forward suggest that there was somewhat stereoscopic vision, i.e., an overlap in the visual field of the animal.
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The higher the spatial frequency, which involves more complex objects within the visual field, the less likely there will be saccadic suppression.Wolf, W., Hauske, G., & Lupp, U. (1978). How presaccadic gratings modify postsaccadic modulation transfer function. Visual Research, 18, 1173-1179.
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The Men's 100 metres, T13 was held on January 23 and 24 T13 = visual impairment: visual acuity ranges from 2/60 to 6/60 and/or has a visual field of more than 5 degrees and less than 20 degrees.
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The Men's 400 metres, T13 was held on January 28 and 29 T13 = visual impairment: visual acuity ranges from 2/60 to 6/60 and/or has a visual field of more than 5 degrees and less than 20 degrees.
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Additional support for the Prioritized processing hypothesis was provided by studies investigating the visual extinction deficit. People suffering from this deficit can perceive a single stimulus in either side visual field if it is presented alone but are unaware of the same stimulus in the visual field opposed to the lesional side, if another stimulus is presented simultaneously on the lesional side. Emotion has been found to modulate the magnitude of the visual extinction deficit, so that items that signal emotional relevance (e.g., spiders) are more likely to be processed in the presence of competing distractors than nonemotional items (e.g.
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The visual pathway consists of structures that carry visual information from the retina to the brain. Lesions in that pathway cause a variety of visual field defects. In the visual system of human eye, the visual information processed by retinal photoreceptor cells travel in the following way: Retina→Optic nerve→Optic chiasm (here the nasal visual field of both eyes cross over to the opposite side)→Optic tract→Lateral geniculate nucleus→Optic radiation→Primary and secondary visual cortices. The type of field defect can help localize where the lesion is located (see picture given in infobox).
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Cross-fixation congenital esotropia, also called Cianci's syndrome is a particular type of large-angle infantile esotropia associated with tight medius rectus muscles. With the tight muscles, which hinder adduction, there is a constant inward eye turn. The patient cross-fixates, that is, to fixate objects on the left, the patient looks across the nose with the right eye, and vice versa. The patient tends to adopt a head turn, turning the head to the right to better see objects in the left visual field and turning the head to the left to see those in the right visual field.
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The gaze-contingent technique is the basis of various experimental paradigms, each of them allowing to investigate specific cognitive processes. In the moving window paradigm only the part of the visual field around the gaze location (foveal information) is displayed normally, the surrounding part of the visual field (extrafoveal and peripheral information) being altered (removed for visual scenes or replaced by chains of X in reading). The moving mask paradigm is a reverse technique in comparison with the moving window paradigm. It dynamically obscures central vision (or replaces letters with X in reading), permitting only extrafoveal information use.
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The modern goals of glaucoma management are to avoid glaucomatous damage and nerve damage, and preserve visual field and total quality of life for patients, with minimal side-effects. This requires appropriate diagnostic techniques and follow-up examinations, and judicious selection of treatments for the individual patient. Although intraocular pressure (IOP) is only one of the major risk factors for glaucoma, lowering it via various pharmaceuticals and/or surgical techniques is currently the mainstay of glaucoma treatment. A review of people with primary open-angle glaucoma and ocular hypertension concluded that medical IOP-lowering treatment slowed down the progression of visual field loss.
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Optic ataxia or visuomotor ataxia is a clinical problem associated with damage to the occipital–parietal cortex in humans, resulting in a lack of coordination between the eyes and hand. It can affect either one or both hands and can be present in part of the visual field or the entire visual field. Optic ataxia has been often considered to be a high-level impairment of eye–hand coordination resulting from a cascade of failures in the sensory to motor transformations in the posterior parietal cortex. Visual perception, naming, and reading are still possible, but visual information cannot direct hand motor movements.
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Visual hierarchy, according to Gestalt psychology, is a pattern in the visual field wherein some elements tend to "stand out," or attract attention, more strongly than other elements, suggesting a hierarchy of importance. While it may occur naturally in any visual field, the term is most commonly used in design (especially graphic design and Cartography), where elements are intentionally designed to make some look more important than others. This order is created by the visual contrast between forms in a field of perception. Objects with highest contrast to their surroundings are recognized first by the human mind.
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It is usually accepted that the primate superior colliculus is unique among mammals, in that it does not contain a complete map of the visual field seen by the contralateral eye. Instead, like the visual cortex and lateral geniculate nucleus, each colliculus represents only the contralateral half of the visual field, up to the midline, and excludes a representation of the ipsilateral half.Lane et al., 1973 This functional characteristic is explained by the absence, in primates, of anatomical connections between the retinal ganglion cells in the temporal half of the retina and the contralateral superior colliculus.
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He is currently working on an extension of Construction Grammar called Sign-Based Construction Grammar, authoring a book on this topic with Charles J. Fillmore, Ivan Sag and Laura Michaelis. Since 2005 Kay has returned to experimental testing of the Sapir- Whorf hypothesis and his findings show that taking into account brain lateralization allows another perspective on the debate. More specifically he proposed that "Whorf hypothesis is supported in the right visual field but not the left". Gilbert AL, Regier T, Kay P, Ivry RB, Whorf hypothesis is supported in the right visual field but not the left, Proc. Natl. Acad.
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This effect has been seen in research involving elderly subjects when compared to young controls, in glaucoma patients compared to age matched controls, cataract patients pre and post surgery, and even something as simple as wearing safety goggles. Monocular vision (one eyed vision) has also been shown to negatively impact balance, which was seen in the previously referenced cataract and glaucoma studies, as well as in healthy children and adults. According to Pollock et al. (2010) stroke is the main cause of specific visual impairment, most frequently visual field loss (homonymous hemianopia- a visual field defect).
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350px Retinotopy (from Greek τόπος, place) is the mapping of visual input from the retina to neurons, particularly those neurons within the visual stream. For clarity, 'retinotopy' can be replaced with 'retinal mapping', and 'retinotopic' with 'retinally mapped'. Visual field maps (retinotopic maps) are found in many mammalian brains, though the specific size, number, and spatial arrangement of these maps can differ considerably between species. Retinotopic maps in cortical areas other than V1 are typically more complex, in the sense that adjacent points of the visual field are not always represented in adjacent regions of the same area.
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This is because the image seen in the left visual field is sent only to the right side of the brain (see optic tract), and most people's speech-control center is on the left side of the brain. Communication between the two sides is inhibited, so the patient cannot say out loud the name of that which the right side of the brain is seeing. A similar effect occurs if a split-brain patient touches an object with only the left hand while receiving no visual cues in the right visual field; the patient will be unable to name the object, as each cerebral hemisphere of the primary somatosensory cortex only contains a tactile representation of the opposite side of the body. If the speech-control center is on the right side of the brain, the same effect can be achieved by presenting the image or object to only the right visual field or hand.
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The hall's far end is described as the central axis of the building's main visual field. Plans for an organic restaurant by architects Gilles & Boissier include using an adjacent garden as a source for menu requirements; Café de la Villette is in size.
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The Men's 400 metres, T12 was held on January 22 and 23 T12 = visual impairment - may be able to recognise the shape of a hand and have a visual acuity of 2/60 and/or visual field of less than 5 degrees.
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Pierre Schoendoerffer was elected at the Académie des Beaux-Arts' Section VII: Artistic creation in the cinema and the audio-visual field, Seat#4, on 23 March 1988, replacing Guillaume Gillet. He is president of the Académie des Beaux-Arts since 2001.
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Mind machines include flashing light devices, which are similar to the Brion Gysin dreamachine in that both produce a flickering visual field. Unlike flashing light devices, the dreamachine can be used by several people at once, but has few, if any, technical features.
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Commonly posterior colobomata affect the inferior retina, with resultant deficit in the superior visual field. Other conditions can be associated with a coloboma. Sometimes, the eye may be reduced in size, a condition called microphthalmia. Glaucoma, nystagmus, scotoma, or strabismus may also occur.
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Figure 4 - Analyser Printout 1: Reliability Indices 2: Numerical Display 3: Grey Scale 4: Total Deviation 5: Probability Display 6: Pattern Deviation 7: Global Indices 8: Glaucoma Hemifield Test 9: Visual Field Index After reliability is determined, the remaining data is assessed.
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Optic neuropathy, nonarteritic anterior ischemic optic neuropathy (N-AION), occurs in 1-2% of people and is not dosage dependent. Bilateral optic disc swelling and mild and reversible visual field defects can also occur. Loss of eyelashes has been linked to amiodarone use.
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This is generally followed by loss of cone photoreceptor cells. Diagnosis is by an examination of the retina finding dark pigment deposits. Other supportive testing may include an electroretinogram, visual field testing, or genetic testing. There is currently no cure for retinitis pigmentosa.
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In order for an illusory conjunction to occur, the two objects that are not the focus of attention need to be within the visual field. The closer two objects are, the more likely the illusory conjunction is to occur.Cohen, A., & Ivry, R. (1989).
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The term "hemiachromatopsia" has been used to denote patients who experience loss of color in only one hemisphere of the visual field. However, as applied to achromatopia resulting from brain trauma, the term is incomplete in characterizing the often-complex nature of the vision loss.
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Since the left hemisphere is responsible for language, this implies that sign movement is linguistically salient. The movement processed on the left side (language) implies that the right visual field is stronger in deaf and hearing ASL due to the hemispheric association being contralateral.
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Serious complications of cataract surgery include retinal detachment and endophthalmitis. In both cases, patients notice a sudden decrease in vision. In endophthalmitis, patients often describe pain. Retinal detachment frequently presents with unilateral visual field defects, blurring of vision, flashes of light, or floating spots.
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The Analyser currently utilises the Swedish Interactive Thresholding Algorithm (SITA); a formula which allows the fastest and most accurate visual field assessment to date. Results are then compared against an age-matched database which highlights unusual and suspicious vision loss, potentially caused by pathology.
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Uncontrolled glaucoma typically leads to visual field loss and ultimately blindness. Uveoscleral outflow of aqueous humour can be increased with prostaglandin agonists, while trabecular outflow is increased by M3 agonists. Fluid production can be decreased by beta blockers, alpha2-agonists, and carbonic anhydrase inhibitors.
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Macdonald Critchley, "Modes of reaction to central > blindness", in Critchley, 1979, p. 156 Anton syndrome may be thought of ideally as the opposite of blindsight, blindsight occurring when part of the visual field is not consciously experienced, but some reliable perception does in fact occur.
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Corrective visual aids and personalized vision therapy provided by Low Vision Specialists may help patients correct slight disturbances in visual acuity and optimize their remaining visual field. Support groups, vision insurance, and lifestyle therapy are additional useful tools for those managing progressive visual decline.
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Amsler grid, Chart 1 There are 7 types of amsler grid charts. All the charts measures 10 cm × 10 cm in size, which can be used to measure central 20 degree visual field when kept at a distance of 33 cm from the eye.
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Visual input from the macula occupies a substantial portion of the brain's visual capacity. As a result, some forms of visual field loss that occur without involving the macula are termed macular sparing. (For example, visual field testing might demonstrate homonymous hemianopsia with macular sparing.) In the case of occipitoparietal ischemia owing to occlusion of elements of either posterior cerebral artery, patients may display cortical blindness (which, rarely, can involve blindness that the patient denies having, as seen in Anton's Syndrome), yet display sparing of the macula. This selective sparing is due to the collateral circulation offered to macular tracts by the middle cerebral artery.
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Lee, C, Rohrer, W, & Sparks, D. (1988). Population coding of saccadic eye movements by neurons in the superior colliculus. Nature, 332(6162), 357-360. It has been found that activation of specific cells is directed by where objects in the environment are located in the visual field.
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Binasal hemianopsia is the medical description of a type of partial blindness where vision is missing in the inner half of both the right and left visual field. It is associated with certain lesions of the eye and of the central nervous system, such as congenital hydrocephalus.
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The main features are seen on fundus examination, just before or subsequent to the onset of visual loss. A pupillary defect may be visible in the acute stage as well. Examination reveals decreased visual acuity, loss of color vision and a cecocentral scotoma on visual field examination.
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This is a fairly deep state. At this level, thoughts visually manifest as objects or environments. When this level is reached, the CEV noise seems to calm down and fade away, leaving behind an intense flat ordered blackness. The visual field becomes a sort of active space.
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David B. Henson. in people who have lost the ability to fixate on an object or light source. The main difference with traditional perimetry instruments is that, microperimetry includes a system to image the retina and an eye tracker to compensate eye movements during visual field testing.
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After his surgery, he was brought in again for testing with Gazzaniga in which stimuli such as letters and light bursts were flashed to the left and right visual fields. The stimuli flashed to the right visual field were processed by the brain’s left hemisphere, which contains the language center, so he was able to press a button to indicate he saw the stimulus and could verbally report what he had seen. However, when the stimuli were flashed to the left visual field, and thus the right hemisphere, he would press the button, but could not verbally report having seen anything. When they modified the experiment to have him point to the stimulus that was presented to his left visual field and not have to verbally identify it, he was able to perform this task accurately.Wolman, David (14 March 2012), “The Split Brain: A Tale of Two Halves”, Nature 483: 260–263(2011), "Interview with Michael Gazzaniga", Annals of the New York Academy of Sciences 1224: 1–8 Patient W.J.’s divided corpus callosum could also cause conflicts between the hemispheres.
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Visual field defects may be one of the first signs of non-functional pituitary tumor. These are much less frequent than functional adenomas. Systemic hormonal aberrations such as Cushing’s syndrome, galactorrhea and acromegaly usually predate the compressive signs. Pituitary tumors often encroach upon the middle chiasm from below.
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Tobacco amblyopia is a form of toxic amblyopia caused by tobacco containing cyanide. Tobacco amblyopia is marked by a gradual impairment of vision characterised by visual field defects and hindered central vision. Methyl alcohol amblyopia occurs through acute poisoning by methyl alcohol and may lead to complete blindness.
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Archives of Ophthalmology 126(5):657-664 Under this grant Chadwick Optical also designed and produced a cosmetically acceptable permanent version of this concept in a prescription lens. An improved version of the Peli Lens expanding the visual field by 30 degrees is available. Clinical trial results are pending.
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Surround suppression is also modulated by attention. By training monkeys to attend to certain areas of their visual field, researchers have studied how directed attention can enhance the suppressive effects of stimuli surrounding the area of attention. Similar perceptual studies have been performed on human subjects as well.
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Pöppel E., Long-range colour- generation interactions across the retina. Nature, 1986, 320(6062): 523-525.Pöppel E, Stoerig P, Logothetis N, Fries W, Boergen KP, Oertel W, Zihl J, Plasticity and rigidity in the representation of the human visual field. Experimental Brain Research, 1987, 68(2): 445-448.
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In 1911, Potzl and Redlich reported a 58-year-old female patient with bilateral damage to her posterior brain. She described motion as if the object remained stationary but appeared at different successive positions. Additionally, she also lost a significant amount of her visual field and had anomic aphasia.
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Hélio Pires 2012, pp. 239-241. A series of early medieval rock castles placed atop hills and mountains with large visual field over the ocean, extending along the coasts of Galicia, have been tentatively idenfified as temporary shelters and watchtowers built by local communities or lords against Norse raids..
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In March 1972, Dent published an article in the Annals of the Association of American Geographers entitled Visual Organization and Thematic Map Communication. In the article, he referenced studies that documented the misinterpretation of the information on thematic maps by map readers. Dent believed that cartographers should use the principles of the figure-ground relationship to better organize the visual field. He explained that “the visual field has two areas; the area that stands out is the figure, and the remainder is the ground” and “to improve communication, the important intellectual elements in the map should appear as figures.”Borden D. Dent, “Visual Organization and Thematic Map Communication,” Annals of the Association of American Geographers 62, no.
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The C1 component typically peaks anywhere from 50–100ms and its polarity and scalp distribution are dependent on where the stimulus is presented (Jeffreys & Axford, 1972; Mangun, Hillyard, & Luck, 1993). Roughly speaking, the C1 has a negative polarity if the stimuli is presented in the upper half of the visual field (when using a mastoid reference) but it has a positive polarity if the stimuli is presented in the lower half of the visual field. The C1 scalp distribution is fairly broad with greatest polarity typically along the occipito-parietal sites (Mangun et al., 1993), although the scalp can be lateralized with greater polarity along the occipito-parietal sites contralateral to the stimulus (Jeffreys & Axford, 1972).
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The patient's left hand was put under a partition and then the patient was asked to draw with their left hand what they had been shown. The patients would draw what they had seen in their left visual field, but when asked what they had drawn would describe what had been shown to their right visual field. These tests proved that when the corpus callosum is severed, it breaks the connection between the left and right hemispheres, making them unable to communicate with each other. Not only are they unable to communicate with each other, but also without the corpus callosum connecting them one hemisphere has no idea that the other hemisphere even exists.
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Category three refers to malformations so severe that their dilated vessels no longer distinguish between artery and vein, and the patient has a significantly increased risk of vision loss. Since the retinal lesions categorized vary from large vascular malformations that affect a majority of the retina to malformations that are barely visible, the lesions can cause a wide range of symptoms, including decrease in visual sharpness, proptosis, pupillary defects, optic nerve degeneration, and visual field defects. The most common type of visual field impairment due to AVMs is homonymous hemianopia, which is usually unilateral. Central nervous system (CNS) symptoms of Bonnet–Dechaume–Blanc syndrome are highly dependent on the locations and sizes of cerebral AVMs.
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Patients and their primary care physicians must be made fully aware of the ophthalmic risks and the need for regular screening examinations to detect retinal toxicity at an early stage. Baseline evaluation for patients beginning treatment with a chloroquine derivative should include a complete eye examination by an eye care professional, retinal photography for follow-up comparisons, and Visual field testing with a white pattern. Central visual field assessment should test the central 10° of vision with a white test target (such as Humphrey 10-2 program). In patients at risk or those with unclear presentation, optical coherence tomography (loss of IS/OS junctions), fundus autofluorescence (focal hyper or hypoautofluorescence), and multifocal electroretinography (paracentral depressions) may be obtained.
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Funduscopic photo left eye centered on the optic disc A person with hypopyon which can be seen in anterior uveitis in a person with Behçet's disease Inflammatory eye disease can develop early in the disease course and lead to permanent vision loss in 20 percent of cases. Ocular involvement can be in the form of posterior uveitis, anterior uveitis, or retinal vasculitis. Anterior uveitis presents with painful eyes, conjuctival redness, hypopyon, and decreased visual acuity, while posterior uveitis presents with painless decreased visual acuity and visual field floaters. A rare form of ocular (eye) involvement in this syndrome is retinal vasculitis which presents with painless decrease of vision with the possibility of floaters or visual field defects.
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Many brain structures that are responsive to visual input, including much of the visual cortex and visual nuclei of the brain stem (such as the superior colliculus) and thalamus (such as the lateral geniculate nucleus and the pulvinar), are organized into retinotopic maps, also called visual field maps. Areas of the visual cortex are sometimes defined by their retinotopic boundaries, using a criterion that states that each area should contain a complete map of the visual field. However, in practice the application of this criterion is in many cases difficult. Those visual areas of the brainstem and cortex that perform the first steps of processing the retinal image tend to be organized according to very precise retinotopic maps.
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In general, the prognosis for retinal migraine is similar to that of migraine headache with typical aura. As the true incidence of retinal migraine is unknown, it is uncertain whether there is a higher incidence of permanent neuroretinal injury. The visual field data suggests that there is a higher incidence of end arteriolar distribution infarction and a higher incidence of permanent visual field defects in retinal migraine than in clinically manifest cerebral infarctions in migraine with aura. One study suggests that more than half of reported recurrent cases of retinal migraine subsequently experienced permanent visual loss in that eye from infarcts, but more recent studies suggest such loss is a relatively rare side effect.
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Psychology Press. New York. Damage to the parietal lobe results in the syndrome ‘neglect' which is when patients treat part of their body or objects in their visual field as though it never existed. Damage to the left side of the parietal lobe can result in what is called Gerstmann syndrome.
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The most likely evolutionary rationale for this effect is that it enhances edges in the visual field, thus facilitating the recognition of shapes and objects. 192x192pxThis is a different concept from contrast, which by itself refers to one object's difference in color and luminance compared to its surroundings or background.
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There is a direct correspondence from an angular position in the visual field of the eye, all the way through the optic tract to a nerve position in V1 (up to V4, i.e. the primary visual areas. After that, the visual pathway is roughly separated into a ventral and dorsal pathway).
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When searching for prey, each eye moves independently from the other. However, when a prey enters the visual field of one of the eyes, they lock into place focused on the prey.Dore, B., et al. “Growth and Light/Dark Adaptation in Lysiosquillina Maculata (Stomatopoda, Crustacea).” Journal of Biological Research, vol.
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The P1 component is a positive going component that typically begins around 70–90ms with a peak around 80-130ms (Mangun, 1995). Its amplitude maximum is over the lateral occipital scalp, approximately right over the ventrolateral prestriate cortex, contralateral to the visual field in which the stimuli is presented (Mangun et al., 1993).
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" Trends in Neurosciences 13.10(1990): 403-08. Print. More recently, the “elastic net” model has been proposed after studying how the primary visual cortex overlaps multiple visual maps, such as visual field position, orientation, direction, ocular dominance, and spatial frequency.Knudsen, E. I., S. Lac, and S. D. Esterly. "Computational Maps in the Brain.
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Accordingly, simple cell receptive fields exist in a variety of different geometries and sizes for all possible orientation and positions in the visual field. It is presumed that multiple concentric LGN receptive fields converge in a line to develop a single simple receptive field.Kaas, J.H., & Collins, C.E. (2004). The primate visual system.
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The drug is in pregnancy category C; the risks of cysteamine to a fetus are not known but it harms babies in animal models at doses less than those given to people. For eye drops, the most common adverse effects are sensitivity to light, redness, and eye pain, headache, and visual field defects.
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Activation of the lingual gyrus has been shown in selective visual attention studies. Subjects were tasked with memorizing symbols in certain visual fields while ignoring those in others. In some subjects, the lingual gyrus was activated. The hemispheric activation of the structure was dependent on which visual field the subject was focused on.
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The naked human eye is weakly sensitive to polarization, without the need for intervening filters. Polarized light creates a very faint pattern near the center of the visual field, called Haidinger's brush. This pattern is very difficult to see, but with practice one can learn to detect polarized light with the naked eye.
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The result is that connections from the left half of the retina, in both eyes, go to the left side of the brain, whereas connections from the right half of the retina go to the right side of the brain. Because each half of the retina receives light coming from the opposite half of the visual field, the functional consequence is that visual input from the left side of the world goes to the right side of the brain, and vice versa. Thus, the right side of the brain receives somatosensory input from the left side of the body, and visual input from the left side of the visual field. The left and right sides of the brain appear symmetrical, but they function asymmetrically.
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Support of the Sapir-Whorf hypothesis describes instances in which speakers of one language demonstrate categorical perception in a way that is different from speakers of another language. Examples of such evidence are provided below: Regier and Kay (2009) reported evidence that linguistic categories affect categorical perception primarily in the right-eye visual field. The right-eye visual field is controlled by the left hemisphere of the brain, which also controls language faculties. Davidoff (2001) presented evidence that in color discrimination tasks, native English speakers discriminated easier between color stimuli across a determined blue-green boundary than within the same side, but did not show CP when given the same task with Berinmo "nol" and "wor"; Berinmo speakers performed oppositely.
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This classification is borrowed by some other sports, including blind golf who also define the class as "From visual acuity above 20/60 up to visual acuity of 6/60 and/or visual field of above 5 degrees and less than 20 degrees." Para-alpine skiing sport specific versions of this definition include one by the Australian Paralympic Committee which defined this classification as "Athletes with slightly more vision or more than five degrees but less than 20 degrees." The International Paralympic Committee defined B3 for alpine skiing as "From visual acuity above 20/60 up to visual acuity of 6/60 and/or visual field of more than 5 degrees and less than 20 degrees." This classification has parallels in other sports.
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In visual areas, the maps are retinotopic; this means they reflect the topography of the retina, the layer of light- activated neurons lining the back of the eye. In this case too, the representation is uneven: the fovea—the area at the center of the visual field—is greatly overrepresented compared to the periphery. The visual circuitry in the human cerebral cortex contains several dozen distinct retinotopic maps, each devoted to analyzing the visual input stream in a particular way. The primary visual cortex (Brodmann area 17), which is the main recipient of direct input from the visual part of the thalamus, contains many neurons that are most easily activated by edges with a particular orientation moving across a particular point in the visual field.
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The large corpus of studies focused on factors that modulate the amplitude of the visual N1 have provided a wealth of evidence suggesting that, while the visual N1 is a sensory component evoked by any visual stimulus, it also reflects a benefit of correctly allocating attentional resources and that it is a manifestation of an important sensory gating mechanism of attention. When attention is focused on areas of the visual field in which relevant information is presented (vs. evenly distributed across the visual field or focused on an area in which relevant information is not presented), the amplitude of the N1 is largest and indicates a benefit of correctly allocating attentional resources.Luck, S.J, Hillyard, S.A., Mouloua, M., Woldorff, M.G., Clark, V.P., & Hawkins, H.L. (1994).
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In fact, studies about unilateral neglect had started in the late 19th century, but not until a century later that it became a major topic in neurology. However, previous studies mainly focused on other aspects of unilateral neglect, like the visual aspect. For visual neglect, patients would ignore one side of their visual field.
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Bitemporal hemianopsia, is the medical description of a type of partial blindness where vision is missing in the outer half of both the right and left visual field. It is usually associated with lesions of the optic chiasm, the area where the optic nerves from the right and left eyes cross near the pituitary gland.
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The Institute offers fee-for-service and charitable eye care. Part of its mission is to provide universal eye care in the Portland, Oregon, area. The Institute also trains post-graduate professionals and conducts research. Scientists from Devers have refined how to interpret visual field testing, a standard part of the assessment of glaucoma.
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Abrupt painless loss of vision in the visual field corresponding to territory of the obstructed artery is the typical history of presentation. Patients can typically define the time and extent of visual loss precisely. Retinal whitening that corresponds to the area of ischemia is the most notable finding. In chronic phase the retinal whitening disappears.
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Prism adaptation is a sensory-motor adaptation that occurs after the visual field has been artificially shifted laterally or vertically. It was first introduced by Hermann von Helmholtz in late 19th-century Germany as supportive evidence for his perceptual learning theory (Helmholtz, 1909/1962).Helmholtz, H. E. F. von (1909/1962). Treatise on Physiological Optics.
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If the papilledema has been longstanding, visual fields may be constricted and visual acuity may be decreased. Visual field testing by automated (Humphrey) perimetry is recommended as other methods of testing may be less accurate. Longstanding papilledema leads to optic atrophy, in which the disc looks pale and visual loss tends to be advanced.
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For example, when a person pays attention to something in the left side of the visual field, an N2pc appears as a greater negativity over the right posterior areas of the brain than the left. MEG has been used to localize the N2pc primarily to lateral extrastriate cortex and inferotemporal visual areas, such as V4.
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Different degrees of multisensory integration may occur depending upon the functional relevance of a given modality. Altogether, the interactions of cross-modal seems to be a rather frequent occurrence. The results of these studies underline the relevance of cross-modal integration in enhancing visual processing in neglect patients and in patients with visual field deficits.
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While walking, elderly subjects depend more on foveal vision than do younger subjects. Their walking speed is decreased by a limited visual field, probably caused by a deteriorated peripheral vision. Younger subjects make use of both their central and peripheral vision while walking. Their peripheral vision allows faster control over the process of walking.
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At the onset of symptoms, ophthalmoscope examination can differentiate AION from PION. If optic nerve head involvement is observed, it is AION. PION does not produce optic atrophy that is observable via ophthalmoscope until four to eight weeks after onset. In addition, AION often shows a characteristic altitudinal defect on a Humphrey Visual Field test.
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Their treatment involves the resection of the optic nerve. The supposed artifactual nature of Wilbrand's knee has implications for the degree of resection that can be obtained, namely by cutting the optic nerve immediately at the junction with the chiasm without fear of potentially resulting visual field deficits. The vast majority of chiasmal syndromes are compressive. Ruben et al.
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At the chiasm, 53% of the axons from the nasal retina cross the midline to join the uncrossed temporal fibers. These nasal fibers carry information from the temporal visual field. Similarly, the temporal fibers transmit images from the nasal field. The two optic tracts, representing the right and left visual fields, emerge posteriorly from the posterior chiasm.
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These cells are less likely to be near neighbours of the same subtype than would occur by chance, resulting in 'exclusion zones' that separate them. Mosaic arrangements provide a mechanism to distribute each cell type evenly across the retina, ensuring that all parts of the visual field have access to a full set of processing elements.
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The optic tract of various clades of insects shows two chiasms, the first and second optic chiasm. In contrast to those in vertebrates, the insect chiasms do not cross the body midline. Rather, the first and second chiasm invert the anterior and posterior visual field. Since there are two chiasms, the retinotopic map is not affected.
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Digit symbol substitution test (DSST) is a neuropsychological test sensitive to brain damage, dementia, age and depression. The test is not sensitive to the location of brain-damage (except for damage comprising part of the visual field). It consists of (e.g. nine) digit-symbol pairs (e.g. 1/-,2/┴ ... 7/Λ,8/X,9/=) followed by a list of digits.
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Oxygen helmets are used in hyperbaric oxygen chambers for oxygen administration. They are transparent, lightweight plastic helmets with a seal that goes around the wearer's neck that looks like a space suit helmet. They offer a good visual field. Light weight plastic hoses provide oxygen to the helmet and remove exhaled gas to the outside of the chamber.
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Some discrepancy exists as to whether acute zonal occult outer retinopathy (AZOOR) is actually considered a white dot syndrome. However, AZOOR may definitely be related to other diseases included in the white dot syndrome group. AZOOR occurs in young to middle age adults and may eventually progress to retinal cell death. Symptoms include acute visual field loss and photopsias.
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They proposed that at some point between the visual input of objects and the response to objects in the visual field there is some competition occurring; competition for representation, analysis, and behavior. This suggests that attention to stimuli makes more demands on processing capacity than unattended stimuli.Desimone, R., & Duncan, J. (1995). Neural Mechanism of Selective Visual Attention.
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Neuropsychological test improvements were noted on tasks that assess visuospatial functioning, although most gains were noted for functional and physical abilities. A patient with congenital deafness exhibited partial Bálint's syndrome symptoms. This patient experienced an inability to perceive simultaneous events in her visual field. She was also unable to fixate and follow an object with her eyes.
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H.J.A. showed top half visual deficits of the entire visual field in both right and left eyes. Lower visual fields showed normal patterns to the stimulus. Through the first experiment, the patient showed that tactile presentation of an object helped H.J.A. significantly in identifying an object. When the object was presented only visually, the patient struggled and showed difficulty.
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A number of businesses and government services offer discounted rates for those who are blind or visually impaired upon presentation of a CNIB identification card. The card is offered exclusively to Canadians who are legally blind and registered at CNIB, with 20/200 vision in the best eye with correction or a visual field of 20 degrees or less.
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This test is able to detect whether a person may be nearsighted or farsighted. These conditions occur when the light rays entering the eye are unable to converge on a single spot on the retina. Both refractive errors require corrective lenses in order to cure blurriness of vision. Visual field tests detect any gaps in peripheral vision.
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This behavior of the blood cells in the capillaries of the retina has been directly observed in human subjects by adaptive optics scanning laser ophthalmoscopy, a real time imaging technique for examining retinal blood flow. The dots will not appear at the very center of the visual field, because there are no blood vessels in the foveal avascular zone.
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A pathological visual illusion is a distortion of a real external stimulus and are often diffuse and persistent. Pathological visual illusions usually occur throughout the visual field, suggesting global excitability or sensitivity alterations. Alternatively visual hallucination is the perception of an external visual stimulus where none exists. Visual hallucinations are often from focal dysfunction and are usually transient.
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At 2 deg eccentricity, for example, acuity is half the foveal value. Note that visual acuity is a measure of how well small details are resolved in the very center of the visual field; it does not tell us how larger patterns are recognized. Visual acuity alone thus cannot determine the overall quality of visual function.
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This technology covers entire 360 degree, approximately entire sphere. Omnidirectional cameras are used where large visual field coverage is needed, such as in panoramic photography. This camera is used in this movie to shoot a song and few scenes. Art direction team has erected 17 sets in and around Chennai to make simultaneous filming process and to save time.
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A visual field map of the primary visual cortex and the numerous extrastriate areas. The primary visual cortex V1 sends visual information to the extrastriate cortical areas for higher order visual processing. These extrastriate cortical areas are located anterior to the occipital lobe. The main ones are designated as visual areas V2, V3, V4, and V5/MT.
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Palinopsia necessitates a full ophthalmologic and neurologic history and physical exam. Hallucinatory palinopsia warrants automated visual field testing and neuroimaging since the majority of hallucinatory palinopsia is caused by posterior cortical lesions and seizures. It is generally easy to diagnose the underlying cause of hallucinatory palinopsia. The medical history typically includes concerning symptoms, and neuroimaging usually reveals cortical lesions.
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Amborella has emerged as of great interest to plant systematists due of recent molecular phylogenetic analyses. There are many epiphytes and large, hanging mossy formations, giving a surreal and ghostly effect. Moisture is abundant, creating a moist, hygrophilous environment with great visual appeal, in the form of mists, sprays, ponds and streams that permeate the entire visual field.
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Due to the functional mapping of the corpus callosum, a partial callosotomy has less detrimental effects because it leaves parts of the corpus callosum intact. There is little functional plasticity observed in partial and complete callosotomies on adults, the most neuroplasticity is seen in young children but not in infants. It is known that when the corpus callosum is severed during an experimental procedure, the experimenter can ask each side of the brain the same question and receive two different answers. When the experimenter asks the right visual field/left hemisphere what they see the participant will respond verbally, whereas if the experimenter asks the left visual field/right hemisphere what they see the participant will not be able to respond verbally but will pick up the appropriate object with their left hand.
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Hemispherectomy or hemispherotomy involves removal or a functional disconnection of most, or all of, one half of the brain typically leaving the basal ganglia and thalamus. It is reserved for people with the most catastrophic epilepsies, such as those due to Rasmussen's encephalitis. If the surgery is performed on very young patients (2–5 years old), then the remaining hemisphere may acquire some motor control of the ipsilateral body due to neuroplasticity; in older patients, paralysis results on the side of the body opposite to the part of the brain that was removed with less prospect for recovery. A visual field defect is an unavoidable side effect, typically involving a homonymous hemianopia involving loss of the half of the visual field on the same side of the disconnected brain.
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The monkeys performed identically to humans on the test, getting them right almost every time. This showed that the monkey's ability to detect movement is separate from their ability to consciously detect an object in their deficit visual field, and gave further evidence for the claim that damage to the striate cortex plays a large role in causing the disorder. Several years later, another study compared and contrasted the data collected from monkeys and that of a specific human patient with blindsight, GY. GY's striate cortical region was damaged through trauma at the age of eight, though for the most part he retained full functionality, GY was not consciously aware of anything in his right visual field. In the monkeys, the striate cortex of the left hemisphere was surgically removed.
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When steadily fixating the central dot for many seconds, the peripheral annulus will fade and will be replaced by the colour or texture of the background. In vision, filling-in phenomena are those responsible for the completion of missing information across the physiological blind spot, and across natural and artificial scotomata. There is also evidence for similar mechanisms of completion in normal visual analysis. Classical demonstrations of perceptual filling-in involve filling in at the blind spot in monocular vision, and images stabilized on the retina either by means of special lenses, or under certain conditions of steady fixation. For example, naturally in monocular vision at the physiological blind spot, the percept is not a hole in the visual field, but the content is “filled-in” based on information from the surrounding visual field.
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This is consistent with other pterygotids, such as Acutiramus, and has been interpreted as indicating that adult Jaekelopterus lived in darker environments, such as in deeper water. Trace fossil evidence of eurypterids also supports such a conclusion, indicating that eurypterids migrated to nearshore environments to mate and spawn. Jaekelopterus had a frontally overlapping visual field, e.g. stereoscopic vision, typical of predatory animals.
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Glaucoma is a group neurodegenerative diseases characterized by features including morphological changes in the optic nerve head and therefore in the visual fields of the patients. There are two main types; open-angle and closed-angle glaucoma. The loss of RGCs (retinal ganglion cells) and their axons results in visual field loss. Increasing evidence also supports the existence of compartmentalized degeneration in synapses.
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Peripheral vision of the human eye. Vision span or perceptual span is a controversial concept referring to the angular span (vertically and horizontally), within which the human eye has sharp enough vision to perform an action accurately (reading or face recognition). The visual field of the human eye spans approximately 120 degrees of arc. However, most of that arc is peripheral vision.
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Utilization behavior patients have difficulty resisting the impulse to operate or manipulate objects which are in their visual field and within reach.Lhermitte, F. (1986) Human autonomy and the frontal lobes. Part II: Patient behavior in complex and social situations: the 'environmental dependency syndrome'. Ann. Neurol. 19, 335–343 Characteristics of UB include unintentional, unconscious actions triggered by the immediate environment.
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If tested in the prodromal phase, CSF pleocytosis is found in more than 80%, mainly lymphocytes. This pleocytosis resolves in about 8 weeks even if chronic uveitis persists. Functional tests may include electroretinogram and visual field testing. Diagnostic confirmation and an estimation of disease severity may involve imaging tests such as retinography, fluorescein or indocyanine green angiography, optical coherence tomography and ultrasound.
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Nature Neuroscience, 14(7), 919-925. The ideal case takes two layers of perfect hexagonal lattices of the on-center and off-center receptive fields of the RGCs. These two layers are superimposed on each other with an angled offset that produces a periodic interference pattern. This pattern produces dipoles of these RGCs that have a preferred orientation scattered throughout the visual field.
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Within the fovea is a region devoid of retinal blood vessels known as the foveal avascular zone (FAZ). The geometric centre of the FAZ is often taken to be the centre of the macula and thus the point of fixation. It is an important landmark in Fluorescein angiography. Its diameter is 0.5mm, the central 1.5 degrees of an individual's Visual field.
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An ophthalmologist may use a Series of imaging techniques. A test called flourescein angiography uses a special dye and camera to study blood flow in the back layers of the eye. When a person has MFC, lesions in the eye will appear as fluorescent spots. Visual field tests may also show an enlarged blind spot or a decrease in visual clarity.
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CPEO is a slowly progressing disease. It may begin at any age and progresses over a period of 5–15 years. The first presenting symptom of ptosis is often unnoticed by the patient until the lids droop to the point of producing a visual field defect. Often, patients will tilt the head backwards to adjust for the slowly progressing ptosis of the lids.
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Animal Science. 62: 301–308. In some breeds, unshorn facial wool can limit the visual field; in some individuals, this may be enough to cause "wool blindness". In 60 Merinos, visual fields ranged from 219.1° to 303.0°, averaging 269.9°, and the binocular field ranged from 8.9° to 77.7°, averaging 47.5°; 36% of the measurements were limited by wool,Hutson, G. D. 1980.
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This is especially observed with the migration of photoreceptors in later stages of development. The eyes are also not attached to any muscles, which restricts them from moving. Instead, the beetle scans its visual field by moving its head from side to side. The larvae eyes are mapped to six distinct neuropils (clusters of interwoven nerves) that function as the optic lobe.
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Trends Cogn. Sci. 6, 176–184 detail findings that buildings and faces require processing at different resolutions in order to be recognised - face recognition requires the analysis of fine detail, while buildings can be recognised using larger scale feature integration. As a result, faces are associated with central visual field processing while buildings are processed more peripherally. Malach et al.
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Altered experiences of arousal are associated with both anxiety and depression. Depression can influence a person's level of arousal by interfering with the right hemisphere's functioning. Arousal in women has been shown to be slowed in the left visual field due to depression, indicating the influence of the right hemisphere. Arousal and anxiety have a different relationship than arousal and depression.
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Native signers do not look at their conversation partner's hands. Instead, their gaze is fixated on the face. Because peripheral vision is not as focused as the center of the visual field, signs articulated near the face allow for more subtle differences in finger movement and location to be perceived. Unlike spoken languages, sign languages have two identical articulators: the hands.
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Orientation selectivity is expressed by cells within the visual cortex, when such cells increase impulse or signal activity for specific oriented degree of shape presented within the visual field. Orientation selectivity can also be expressed by simple cells if the orientation of a stimulus is orthogonal to the preferred degree of orientation, which results in the inhibition of impulse activity.
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The Analyser projects a series of white light stimuli of varying intensities (brightness), throughout a uniformly illuminated bowl. The patient uses a handheld button that they press to indicate when they see a light. This assesses the retina's ability to detect a stimulus at specific points within the visual field. This is called retinal sensitivity and is recorded in 'decibels' (dB).
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Retinal detachment is a disorder of the eye in which the retina separates from the layer underneath. Symptoms include an increase in the number of floaters, flashes of light, and worsening of the outer part of the visual field. This may be described as a curtain over part of the field of vision. In about 7% of cases both eyes are affected.
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For example, observers were able to attend simultaneously to two different targets located in opposite hemifields. Research has even suggested that humans are able to focus attention across two to four locations in the visual field. Another perspective is that spatial attention can be split only under certain conditions. This perspective suggests that the splitting of spatial attention is flexible.
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Schiller, J., Dietrich, T.J., Lorch, L., Skalej, M., Braun, C., Schiefer, U. (1998/1999). Homonymous Visual Field Defects Perimetric findings and corresponding neuro-imaging results. The Hague, the Netherlands: Kugler Publications. For example, they can read fairly well because they can process the entirety of a word presented to their center field of vision like a person with normal vision.
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An exogenous cue is presented outside of the center of focus, usually highlighting the left or right box presented on the screen. An exogenous cue can also be an object or image in the periphery, a number of degrees away from the centre, but still within the visual angle. This cue relies on visual input from the peripheral visual field.
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Dr Henry (Harry) Moss Traquair, FRSE, PRCSE (1875 – 14 November 1954) was a Scottish ophthalmic surgeon who made important contributions to the science of perimetry and the use of visual field testing in the diagnosis of disease. He was President of the Royal College of Surgeons of Edinburgh in 1939/40 and President of the Ophthalmological Society of the United Kingdom.
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The collagen fibres of the vitreous are held apart by electrical charges. With aging, these charges tend to reduce, and the fibres may clump together. Similarly, the gel may liquefy, a condition known as synaeresis, allowing cells and other organic clusters to float freely within the vitreous humour. These allow floaters which are perceived in the visual field as spots or fibrous strands.
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The prognosis is excellent except in case of complications of choroidal rupture, hemorrhage or pigment epithelial damage, but damage to the macula will result in poorer recovery. The outcome can be worsened in the case of retinal detachment, atrophy or hyperplasia. Visual field defects can occur. In late cases cystoid macular edema sometimes develops which can further lead to macular destruction.
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In order to qualify for service through the NLS, blind people must have vision that is 20/200 or less in the better eye with correcting lenses or whose widest diameter of visual field subtends an angular distance no greater than 20 degrees. People may also qualify for services if they are visually impaired and unable to read standard print materials.
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Hemianopsia, or hemianopia, is a loss of vision or blindness (anopsia) in half the visual field, usually on one side of the vertical midline. The most common causes of this damage are stroke, brain tumor, and trauma.Hemianopia (Hemianopsia) , helpforvisionloss.com This article deals only with permanent hemianopsia, and not with transitory or temporary hemianopsia, as identified by William Wollaston PRS in 1824.
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To compensate for this, patients with trochlear nerve palsies tilt their heads to the opposite side, in order to fuse the two images into a single visual field. The characteristic appearance of patients with fourth nerve palsies (head tilted to one side, chin tucked in) suggests the diagnosis, but other causes must be ruled out. For example, torticollis can produce a similar appearance.
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175 In 1875, Hirschberg coined the term "campimetry" for the measurement of the visual field on a flat surface (tangent screen test) The age of isopter perimetry at webeye.ophth.uiowa.edu and in 1879 he became the first to use an electromagnet to remove metallic foreign bodies from the eye.Manage Account - Modern Medicine at www.ophthalmologytimes.com In 1886, he developed the Hirschberg test for measuring strabismus.
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Hormone secreting pituitary adenomas cause one of several forms of hyperpituitarism. The specifics depend on the type of hormone. Some tumors secrete more than one hormone, the most common combination being GH and prolactin, which present as unexpected bone growth and unexpected lactation (in both men and women). A patient with pituitary adenoma may present with visual field defects, classically bitemporal hemianopsia.
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The favored explanation for why the center visual field is preserved after large hemispheric lesions is that the macular regions of the cortex have a double vascular supply from the middle cerebral artery (MCA) and the posterior cerebral artery (PCA). If there is damage to one vascular pathway, like in the case of a MCA or PCA stroke, there is still another blood supply that the macular portions of the visual cortex can rely on. Vision in the center of the visual field is then preserved whereas vision in peripheral areas is lost due to the resulting infarct. Another possible reason is that the maculae project to both hemispheres, so in the event of a lesion in one hemisphere, the other intact hemisphere will still receive and process visual information from the maculae in both eyes.
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An impairment following damage to a region of the brain does not necessarily imply that the damaged area is wholly responsible for the cognitive process which is impaired, however. For example, in pure alexia, the ability to read is destroyed by a lesion damaging both the left visual field and the connection between the right visual field and the language areas (Broca's area and Wernicke's area). However, this does not mean one suffering from pure alexia is incapable of comprehending speech—merely that there is no connection between their working visual cortex and language areas—as is demonstrated by the fact that pure alexics can still write, speak, and even transcribe letters without understanding their meaning.More Brain Lesions, Kathleen V. Wilkes Lesions to the fusiform gyrus often result in prosopagnosia, the inability to distinguish faces and other complex objects from each other.
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Less common, but important because they are sometimes reversible or curable by surgery, are scotomata due to tumors such as those arising from the pituitary gland, which may compress the optic nerve or interfere with its blood supply. Rarely, scotomata are bilateral. One important variety of bilateral scotoma may occur when a pituitary tumour begins to compress the optic chiasm (as distinct from a single optic nerve) and produces a bitemporal paracentral scotoma, and later, when the tumor enlarges, the scotomas extend out to the periphery to cause the characteristic bitemporal hemianopsia. This type of visual-field defect tends to be obvious to the person experiencing it but often evades early objective diagnosis, as it is more difficult to detect by cursory clinical examination than the classical or textbook bitemporal peripheral hemianopia and may even elude sophisticated electronic modes of visual-field assessment.
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An impairment following damage to a region of the brain does not necessarily imply that the damaged area is wholly responsible for the cognitive process which is impaired, however. For example, in pure alexia, the ability to read is destroyed by a lesion damaging both the left visual field and the connection between the right visual field and the language areas (Broca's area and Wernicke's area). However, this does not mean one suffering from pure alexia is incapable of comprehending speech—merely that there is no connection between their working visual cortex and language areas—as is demonstrated by the fact that pure alexics can still write, speak, and even transcribe letters without understanding their meaning. Lesions to the fusiform gyrus often result in prosopagnosia, the inability to distinguish faces and other complex objects from each other.
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Yettus disease is a visual disturbance in which objects in the visual field appear to oscillate. The severity of the effect may range from a mild blurring to rapid and periodic jumping. Oscillopsia is an incapacitating condition experienced by many patients with neurological disorders. It may be the result of ocular instability occurring after the oculomotor system is affected, no longer holding images steady on the retina.
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Chiasmal syndrome is the set of signs and symptoms that are associated with lesions of the optic chiasm, manifesting as various impairments of the sufferer's visual field according to the location of the lesion along the optic nerve. Pituitary adenomas are the most common cause; however, chiasmal syndrome may be caused by cancer, or associated with other medical conditions such as multiple sclerosis and neurofibromatosis.
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Phosphenes have been produced by intense, changing magnetic fields, such as with transcranial magnetic stimulation (TMS). These fields can be positioned on different parts of the head to stimulate cells in different parts of the visual system. They also can be induced by alternating currents that entrain neural oscillation as with transcranial alternating current stimulation. In this case they appear in the peripheral visual field.
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The cuneus (Latin for "wedge"; plural, cunei) is a smaller lobe in the occipital lobe of the brain. The cuneus is bounded anteriorly by the parieto- occipital sulcus, inferiorly by the calcarine sulcus. The cuneus (Brodmann area 17) receives visual information from the same-sided superior quadrantic retina (corresponding to contralateral inferior visual field). It is most known for its involvement in basic visual processing.
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During eye evolution there existed an additional convex stadium of the retina (Figure 1, Left), presumably, which explains why today the left visual field is represented in the right hemisphere and vice versa. With the change from convex to concave retinas, the visual input changed sides on the retina, and was represented upside down in addition. During evolution existed a convex stadium of the retina.
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As of 2017, data on optimal treatment was limited. Therapies with hormones is the standard of care, namely adrenocorticotrophic hormone (ACTH), or oral corticosteroids such as prednisone. Vigabatrin is also a common consideration, though there is a risk of visual field loss with long term use. The high cost of ACTH leads doctors to avoid it in the US; higher dose prednisone appears to generate equivalent outcomes.
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The visual field, the area or extent of physical space that is being imaged on the retina, should be distinguished from the perceptual space in which visual percepts are located, which we call visual space. Confusion is caused by the use of Sehraum in the German literature for both. There is no doubt that Ewald Hering and his followers meant visual space in their writings.
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Dysmorphopsia, in a broad sense, is a condition in which a person is unable to correctly perceive objects. It is a visual distortion, used to denote a variant of metamorphopsia in which lines appear wavy. These illusions may be restricted to certain visuals areas, or may affect the entire visual field. It has been associated with meningioma tumors and bilateral lateral occipital corital damage, e.g.
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At first, electronics companies were somewhat leery of working with a supplier that got its start making motors for toy cars. But one after another, brand name manufacturers chose the quality and price of the RF-510G, and the Mabuchi brothers helped bring affordable Japanese radio cassette decks, portable headphone stereo CD players, and numerous other products in the audio visual field, to consumers across the world.
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TCA is defined as the variation in angle between the refracted chief rays for different wavelengths. Chief rays, in this case, refer to rays from a point source that passes through the center of the pupil. Unlike LCA, TCA depends on object location in the visual field and pupil position within the eye. Object location determines the angle of incidence of the selected rays.
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Patients with branch retinal vein occlusion usually have a sudden onset of blurred vision or a central visual field defect. The eye examination findings of acute branch retinal vein occlusion include superficial hemorrhages, retinal edema, and often cotton- wool spots in a sector of retina drained by the affected vein. The obstructed vein is dilated and tortuous. The quadrant most commonly affected is the superotemporal (63%).
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Focused attention Humans have a physiologically limited visual field that must be selectively directed to certain stimuli. Attention is the cognitive process that allows this task to be accomplished and it might be responsible for the phenomenon of wishful seeing. Expectations, desires and fears are among the various factors that help direct attention. Consequently, these cognitive experiences have the opportunity to influence the perceptual experience.
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An elderly couple exhibiting typical signs of physical aging. At the sensory level, changes occur to vision, hearing, taste, touch, and smell, and taste. Two common sensory changes that begin in midlife include our ability to see close objects and our ability to hear high pitches. Other developmental changes to vision might include cataracts, glaucoma, and the loss of central visual field with macular degeneration.
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In children, optic disc drusen are usually buried and undectectable by fundoscopy except for a mild or moderate elevation of the optic disc. With age, the overlying axons become atrophied and the drusen become exposed and more visible. They may become apparent with an ophthalmoscope and some visual field loss at the end of adolescence. ODD can compress and eventually compromise the vasculature and retinal nerve fibers.
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Current consensus among ophthalmologists and optometrists define normal intraocular pressure as that between 10 mmHg and 20 mmHg.webMD - TonometryGlaucoma Overview from eMedicine The average value of intraocular pressure is 15.5 mmHg with fluctuations of about 2.75 mmHg. Ocular hypertension (OHT) is defined by intraocular pressure being higher than normal, in the absence of optic nerve damage or visual field loss.Ocular Hypertension, American Optometric Association.
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In certain split-brain patients who have undergone a corpus callosotomy to treat severe epilepsy, the information from one optic tract does not get transmitted to both hemispheres. For instance, a split- brain patient shown an image in the left visual field will be unable to vocally name what has been seen as the speech-control center is in the left hemisphere of the brain.
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The Peli Lens is a mobility aid for people with homonymous hemianopia. It is also known as “EP” or Expansion Prism concept and was developed by Dr. Eli Peli of Schepens Eye Research Institute in 1999. It expands the visual field by 20 degrees. He tested this concept on several patients in his private practice with great success using 40Δ Fresnel press-on prisms (Peli 2000).
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According to the ‘spotlight’ metaphor, the focus of attention is analogous to the beam of a spotlight. The moveable spotlight is directed at one location and everything within its beam is attended and processed preferentially, while information outside the beam is unattended. This suggests that the focus of visual attention is limited in spatial size and moves to process other areas in the visual field.
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This is contrasted with abstract objects such as mental objects, which exist in the mental world, and mathematical objects. Other examples that are not physical bodies are emotions, the concept of "justice", a feeling of hatred, or the number "3". In some philosophies, like the idealism of George Berkeley, a physical body is a mental object, but still has extension in the space of a visual field.
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Inattentional blindness is the failure to see a stimulus, such as an object that is present in a visual field. However, change blindness is the failure to notice something different about a visual display. Change blindness is a directly related to memory, individuals who experience the effects of change blindness fail to notice something different about a visual display from one moment to the next.Driver, J. (1998).
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Two major cue types are used to analyze attention based on the type of visual input. An endogenous cue is presented in the center of the screen, usually at the same location as the center of focus. It is an arrow or other directional cue pointing to the left or right box on the screen. This cue relies on input from the central visual field.
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A persistence of a visual image of an object in time after the actual object has disappeared. There are two forms of palinopsia, an immediate and a delayed type. In the immediate type the image continually persists in the visual field after actually disappearing. On the other hand, in the delayed type, the image reappears after an interval of minutes to hours after disappearing.
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Profound abnormalities detected with visual field and multifocal electroretinography testing can be observed in the presence of a normal retinal appearance. Retinal examinations are advised for documentation, but visible bull's-eye maculopathy is a late change, and the goal of screening is to recognize toxicity at an earlier stage. Annual screening should begin after 5 years (or sooner if there are unusual risk factors).
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In 1912, Bornstein developed cramps in his hands and legs while breathing oxygen at for 51 minutes. Smith then went on to show that intermittent exposure to a breathing gas with less oxygen permitted the lungs to recover and delayed the onset of pulmonary toxicity. Albert R. Behnke et al. in 1935 were the first to observe visual field contraction (tunnel vision) on dives between and .
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Vesely's argument on the epistemological process of being situated develops in terms of an analogy to the formation of the visual field. And takes the organic ability of sight only as a point of departure to the phenomenon of vision, i.e. what one is able to recognize and know out of visual perception. Accordingly, the natural process of seeing is shown to be a result from learning.
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When the image disparity is astigmatic (cylindrical) and not uniform, images can appear wider, taller, or diagonally different. When the disparity appears to vary across the visual field (field-dependent aniseikonia), as may be the case with an epiretinal membrane or retinal detachment, the aniseikonia cannot fully be corrected with traditional optical techniques like standard corrective lenses. However, partial correction often improves the patient's vision comfort significantly.
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Eye movements are important behaviors for locating and tracking objects in the visual world. Two of the major types of eye movements are saccades and smooth pursuit. Saccades are very rapid and precise eye movements between two positions, and are important in establishing fixation. Smooth pursuit on the other hand, allows the viewer to track a moving object along its trajectory within the visual field.
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Photoreceptors signals color; they only signal the presence of light in the visual field. A given photoreceptor responds to both the wavelength and intensity of a light source. For example, red light at a certain intensity can produce the same exact response in a photoreceptor as the green light of different intensity. Therefore, the response of a single photoreceptor is ambiguous when it comes to color.
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The dorsal stream is involved in spatial awareness and guidance of actions (e.g., reaching). In this it has two distinct functional characteristics—it contains a detailed map of the visual field, and is also good at detecting and analyzing movements. The dorsal stream commences with purely visual functions in the occipital lobe before gradually transferring to spatial awareness at its termination in the parietal lobe.
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Congo the chimpanzee During the late 1950s, biologists began to study the nature of art in humans. Theories were proposed based on observations of non-human primate paintings. Hundreds of such paintings were cataloged by Desmond Morris. Morris and his associate Tyler Harris interpreted these canvas paintings as indications of an intrinsic motivation toward abstract creativity, as expressed through an exploration of the visual field and color.
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The extent of the symptoms and the damage is different from person to person. If a person has complete achromatopsia, then their entire visual field is devoid of colour. A person with dyschromatopsia, or incomplete achromtopsia, has similar symptoms to complete achromatopsia, but to a lesser degree. This can occur in people who had achromatopsia, but the brain recovered from the injury, restoring some colour vision.
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Illusory palinopsia consists of afterimages that are short-lived or unformed, occur at the same location in the visual field as the original stimulus, and are often exposed or exacerbated based on environmental parameters such as stimulus intensity, background contrast, fixation, and movement. Illusory palinopsia symptoms occur continuously or predictably, based on environmental conditions. The term is from Greek: palin for "again" and opsia for "seeing".
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A frequently occurring motor deficit is left-sided hemiparesis (in strokes affecting the motor cortex). A less common motor deficit in this population is dysphagia. Patients with right hemisphere brain damage often display sensory deficits such as left neglect, in which they ignore everything in the left visual field. This neglect can be present throughout many daily activities including reading, writing and self-care activities.
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Some mental control can be exerted over these closed-eye visualizations, but it usually requires a bit of relaxation and concentration to achieve. When properly relaxed it is possible to cause regions of intense black, bright white or even colors such as yellow, green, or pink to appear in the noise. These regions can span the entire visual field, but seem to be fleeting in nature.
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Her recognition time for visual objects and words was slightly higher than the control, but not statistically significant. There was no restriction in her visual field and no scotoma. ;Disturbance of movement vision LM's impression of movement depended on the direction of the movement (horizontal vs vertical), the velocity, and whether she fixated in the center of the motion path or tracked the object with her eyes.
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RC, III-348 ff., 63e. Although Remarks on Colour is considered difficult on account of its fragmentation, his last work, On Certainty (German: Über Gewissheit) is considered his most lucid. One resolution of this difficulty is that Remarks on Colour is really not fragmentary in nature, but a sustained and identifiable argument against the misleading view that colours are features of places in the visual field.
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Chart 1 is the basic version, which is the most familiar and widely used chart among all the charts. In this chart the grid consists of 0.5 cm squares (each for 1° visual field), which totally measures 10 cm X 10 cm size. Most commonly grid is in white color with black background. Grid with black lines in white background is also available (see infobox picture).
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The result of the experiment was the identification of an area in the subject, slightly anterior to the lesioned area in cerebral achromatic patients, that responded to variance in color stimulation. The resolution of the MRI was a limiting factor in identifying areas corresponding to specific colors. The next portion of the study used an electrode implanted in the right hemisphere in the location identified by the fMRI scan as pertaining to color processing. It was found the electrical activity of the area increased when the subject was presented with blue stimuli. The next, and most significant finding of the study, was that when the electrode was used to present an electrical stimulus in the subject’s brain, the subject reported the perception of the color blue. Such a result is consistent with other reports of electrical stimulation in visual field maps eliciting perception of phosphines in subjects’ visual field.
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This word described one of the objects in the tray, so the patient's left hand picked up the object corresponding to the word. When participants were asked about the word and the object in their hand, they claimed they had not seen the word and had no idea why they were holding the object. The right side of the brain had recognized the word and told the left hand to pick it up, but because the right side of the brain cannot speak and the left side of the brain had not seen the word, the patient could not articulate what they had seen. In another series of experiments further examining the lateralization of language in the left and right hemispheres, Sperry presented one object to the left visual field and a different object to the right visual field of the "split-brain" patients.
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While non-secreting, noninvasive pituitary microadenomas are generally considered to be literally as well as clinically benign, there are to date scant studies of low quality to support this assertion. It has been recommended in the current Clinical Practice Guidelines (2011) by the Endocrine Society - a professional, international medical organization in the field of endocrinology and metabolism - that all patients with pituitary incidentalomas undergo a complete medical history and physical examination, laboratory evaluations to screen for hormone hypersecretion and for hypopituitarism. If the lesion is in close proximity to the optic nerves or optic chiasm, a visual field examination should be performed. For those with incidentalomas which do not require surgical removal, follow up clinical assessments and neuroimaging should be performed as well follow-up visual field examinations for incidentalomas that abut or compress the optic nerve and chiasm and follow-up endocrine testing for macroincidentalomas.
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An ESR should be drawn to detect possible giant cell arteritis. Improvement can be determined by visual acuity, visual field testing, and by ophthalmoscopic examination. At a later stage, pan-retinal photocoagulation (PRP) with an argon laser appears effective in reducing the neovascular components and their sequelae. The visual prognosis for ocular ischemic syndrome varies from usually poor to fair, depending on speed and effectiveness of the intervention.
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They have 13 flight feathers, no tail and a small pygostyle. Their gizzard is weak and their caecum is long and narrow. The eye of the kiwi is the smallest relative to body mass in all avian species resulting in the smallest visual field as well. The eye has small specialisations for a nocturnal lifestyle, but kiwi rely more heavily on their other senses (auditory, olfactory, and somatosensory system).
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A 2016 Cochrane Review sought to determine the effectiveness of YAG laser iridotomy versus no laser iridotomy for pigment dispersion syndrome and pigmentary glaucoma, in 195 participants, across five studies. No clear benefits in preventing loss of visual field were found for eyes treated with peripheral laser iridotomy. There was weak evidence suggesting that laser iridotomy could be more effective in lowering intraocular pressure in eyes versus no treatment.
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Sometimes, when looking at rotating three-dimensional silhouettes, they will suddenly appear to change the direction in which they are rotating, even though nothing about the image has changed. This sudden change is because the silhouette lacks any depth cues from shading. Data from an experiment showed that subjects experienced changes more when the image was being processed by their left hemisphere which controls the right side of the visual field.
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Courtship is more or less the same in all Papilionidae. Once a female enters the visual field of a male, the male moves quickly to hover over her so that his wings beat rapidly. The female is then induced to land so that the male can attempt to mate with her. There are various ways in which the male entices the female, including visual, olfactory, tactile, and auditory cues.
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The visual loss depends on which part of the nerve is affected. If the part of the nerve between the eye and the chiasm is compressed, the result is vision loss in one eye. If the part after the chiasm is affected, visual loss on one side of the visual field occurs. Adjacent to the pituitary lies a part of the skull base known as the cavernous sinus.
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The origin corresponds to the point on which the observer is fixating. The polar angle is considered to be zero degrees when a locus is horizontally to the right of the fixation point and to increase to a maximum of 360 degrees going anticlockwise. Distance from the origin is given in degrees of visual angle; it's a measure of eccentricity. Each polar axis is a meridian of the visual field.
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There are two major neural pathways that process the information in the visual field; the ventral stream and the dorsal stream. The two pathways run in parallel and are both working simultaneously. The ventral stream is important for object recognition and often referred to as the “what” system of the brain; it projects to the inferior temporal cortex.Ungerleider, L. G., & Haxby, J. V. (1994). ‘What’ and ‘where’ in the human brain.
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One rare, important feature of the Takayasu's arteritis is ocular involvement in form of visual field defects, vision loss, or retinal hemorrhage. Some individuals with Takayasu's arteritis may present with only late vascular changes, without a preceding systemic illness. In the late stage, weakness of the arterial walls may give rise to localized aneurysms. As with all aneurysms, the possibility of rupture and vascular bleeding is existent and requires monitoring.
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The frontal eye field plays a very important role when it comes to eye movements. Particularly the frontal eye field is responsible for much of the saccadic eye movements that eyes make. Once the frontal eye field is activated by the corollary discharge signal, it sends a predictive signal to the occipital lobe. This signal essentially predicts what the visual field should look like after an eye movement.
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Kline, Holcombe, and Eagleman (2004) confirmed the observation of reversed rotation with regularly spaced dots on a rotating drum. They called this "illusory motion reversal". They showed that these occurred only after a long time of viewing the rotating display (from about 30 seconds to as long as 10 minutes for some observers). They also showed that the incidences of reversed rotation were independent in different parts of the visual field.
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Once the flies begin to flee, the redstart begins to chase. It has been proposed that redstarts exploit two aspects of the visual sensitivity of their prey: sensitivity to the location of the stimulus in the prey's visual field and sensitivity to the direction of stimulus environment. The effectiveness of this pursuit can also be explained by "rare enemy effect", an evolutionary consequence of multi-species predator- prey interactions.
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Despite occupying about 0.01% of the visual field (less than 2° of visual angle), about 10% of axons in the optic nerve are devoted to the fovea. The resolution limit of the fovea has been determined to be around 10,000 points. The information capacity is estimated at 500,000 bits per second (for more information on bits, see information theory) without colour or around 600,000 bits per second including colour.
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Autoimmune retinopathy (AIR) is a rare disease in which the patient's immune system attacks proteins in the retina, leading to loss of eyesight. The disease is poorly understood, but may be the result of cancer or cancer chemotherapy. The disease is an autoimmune condition characterized by vision loss, blind spots, and visual field abnormalities. It can be divided into cancer-associated retinopathy (CAR) and melanoma-associated retinopathy (MAR).
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Vogel, R., Sary, G., Dupont, P., Orban, G. Human Brain Regions Involved in Visual Categorization. Elsevier Science (USA) 2002. After recognizing and categorizing new material entered into the visual field, the brain is ready to begin the encoding process – the process which leads to learning. Multiple brain areas are involved in this process such as the frontal lobe, the right extrastriate cortex, the neocortex, and again, the neostriatum.
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An explanation for this phenomenon is that observers see the critical object in their visual field but fail to process it extensively enough to retain it. Individuals experience inattentional agnosia after having seen the target stimuli but not consciously being able to identify what the stimuli is. It is possible that observers are not even able to identify that the stimuli they are seeing are coherent objects.Neisser, U. (1967).
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Phosphenes are spread out across the visual field in what researchers call "the starry-night effect". Immediately after his implant, Jens was able to use his imperfectly restored vision to drive an automobile slowly around the parking area of the research institute. Unfortunately, Dobelle died in 2004Tuller, David (1 November 2004) Dr. William Dobelle, Artificial Vision Pioneer, Dies at 62. The New York Times before his processes and developments were documented.
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Lateral connections are connections between neurons in the same layer. There are many of these connections in all areas of the visual system, which means that a neuron representing one piece of the visual field can influence a neuron representing another piece. Even within lateral connections, there are potentially different mechanisms at play. Monocular mechanisms, requiring stimulation in only one eye, may drive this effect with stimuli with high spatial frequency.
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When the tectum was removed, orienting behavior disappeared. When the thalamic-pretectal region was removed, avoidance behavior was entirely absent while orienting behavior was enhanced even to predator stimuli. Furthermore, prey-selective properties were impaired both in prey-selective neurons and in prey-catching behavior (Zupanc 2004). Finally, when one half of the thalamic- pretectal region was removed, the disinhibition applied to the entire visual field of the opposite eye.
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It was found compared to some other North American raptors who are more likely to watch for prey on the ground and/or in the open, that the Cooper's hawk had a rather enlarged binocular field.Potier, S., Duriez, O., Cunningham, G. B., Bonhomme, V., O'Rourke, C., Fernández-Juricic, E., & Bonadonna, F. (2018). Visual field shape and foraging ecology in diurnal raptors. Journal of Experimental Biology, 221(14), jeb177295.
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According to Treisman, the first stage of the feature integration theory is the preattentive stage. During this stage, different parts of the brain automatically gather information about basic features (colors, shape, movement) that are found in the visual field. The idea that features are automatically separated appears counterintuitive. However, we are not aware of this process because it occurs early in perceptual processing, before we become conscious of the object.
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This procedure is then repeated at several other locations, until the entire visual field is tested. Threshold static perimetry is generally done using automated equipment. It is used for rapid screening and follow up of diseases involving deficits such as scotomas, loss of peripheral vision and more subtle vision loss. Perimetry testing is important in the screening, diagnosing, and monitoring of various eye, retinal, optic nerve and brain disorders.
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Repeating this enough will establish a boundary of vision for that target. The procedure is repeated using different test lights that are larger or brighter than the original test light. In this way, kinetic perimetry is useful for mapping visual field sensitivity boundaries. It may be a good alternative for patients that have difficulty with automated perimetry, either due to difficulty maintaining constant gaze, or due to cognitive impairment.
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Perception and Psychophysics, 22(1): 54-62. examined amplitude changes in the N1 during a task in which light flashes were concurrently delivered to the left or right visual field in independently random sequences. Subjects were instructed to attend left, attend right, or attend to both fields. Enhancement of the N1 at the occipital site was found when attention was directed to the field in which light flashes were delivered.
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The primary visual cortex (V1) is located in and around the calcarine fissure in the occipital lobe. Each hemisphere's V1 receives information directly from its ipsilateral lateral geniculate nucleus that receives signals from the contralateral visual hemifield. Neurons in the visual cortex fire action potentials when visual stimuli appear within their receptive field. By definition, the receptive field is the region within the entire visual field that elicits an action potential.
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Additionally as stimulus size increased, so did the sparseness. This suggests that the V1 uses sparse code when natural images span the entire visual field. The CRF was defined as the circular area surrounding the locations where stimuli evoked action potentials. They also tested to see if the stimulation of the nCRF increased the independence of the responses from the V1 neurons by randomly selecting pairs of neurons.
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Rod and cone photoreceptors are found on the outermost layer of the retina; they both have the same basic structure. Closest to the visual field (and farthest from the brain) is the axon terminal, which releases a neurotransmitter called glutamate to bipolar cells. Farther back is the cell body, which contains the cell's organelles. Farther back still is the inner segment, a specialized part of the cell full of mitochondria.
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Formed image perseveration refers to a single, stationary object that remains fixed in one's visual field. These pathological afterimages look realistic and have the same color and clarity as the original stimulus. The palinopsia lasts at least 15 seconds, but may persist for hours or days. For example, a patient sees a cat, and an identical copy of the cat remains fixed in the field of view for 30 minutes.
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Palinopsia, which occurs after neurosurgical procedures or cerebrovascular accidents, has been partly attributed to focal cortical irritation. Symptoms are associated with perilesional hyperperfusion, which may reflect focal cortical instability and subsequent hyperactivity. While there are reports of palinopsia from each individual mechanism, there is usually a combination of the aforementioned mechanisms. For example, hallucinatory palinopsia may present in a patient with seizure symptoms and visual field deficits, after a neurosurgical procedure.
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PhD, D.Z.Z., & Israel Hod MD, P.D. (1994). L'homme qui rit: inappropriate laughter and release phenomena of the frontal subdominant lobe. Behavioral Medicine, 20(1), 44-46. Case #2: A 33-year-old man, James Harden, was admitted to the hospital with signs of a putaminal hemorrhage, including dense paralysis on the left side of his body and face, difficulty swallowing, and visual field defects on his left side.
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In addition to the retinal findings, temporal pallor of the optic disc is commonly observed. As expected, visual field testing in cone dystrophy usually reveals a central scotoma. In cases with the typical bull’s-eye appearance, there is often relative central sparing. Because of the wide spectrum of fundus changes and the difficulty in making the diagnosis in the early stages, electroretinography (ERG) remains the best test for making the diagnosis.
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Microperimetry, sometimes called Fundus related perimetry, is a type of visual field testGlaucoma Diagnosis, Structure and function, pp. 83-92. Edited by Robert N. Weinreb and Erik L. Greve. 2004 Kugler Publications, The Hague, The Netherlands which uses one of several technologies to create a "retinal sensitivity map" of the quantity of light perceived in specific parts of the retinaVisual Fields, pp. 1-5. Edited by Oxford University Press.
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Physical examinations showing papilledema, visual field defects, cranial nerves palsy, dysphasia, and focal neurological deficits are evidences for possible tumor. PNETs can also be spotted through computed tomography (CT) and magnetic resonance imaging (MRI). In images produced by MRIs, an irregular augmentation among a solid mass will indicated the presence of tumor. However, the results of MRIs are usually ambiguous in defining the presence for this specific tumor.
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Amsler grid usually help detecting defects in central 20 degrees of the visual field. In the test, the person looks with each eye separately at the small dot in the center of the grid. Patients with macular disease may see wavy lines or some lines may be missing. Amsler grids are supplied by ophthalmologists, optometrists or from web sites, and may be used to test one's vision at home.
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Rolls, E. T. (2008). Memory, attention and decision-making: A unified computational neuro-science approach; Oxford University Press, Oxford. Visual search tasks are commonly used by experimenters to aid the exploration of visual perception. The classical view of visual attention suggests that there are two basic principles: the pre-attentive stage and the attentive stage.Rolls, E. T. (2008). Memory, attention and decision-making: A unified computational neuro-science approach; Oxford University Press, Oxford. In the pre-attentive stage, an individual has an unlimited capacity for perception which is capable of processing information from the entire visual field concurrently. During the attentive stage, the processing of visual information corresponding to local spatial areas takes place.Rolls, E. T. (2008). Memory, attention and decision-making: A unified computational neuro-science approach; Oxford University Press, Oxford. This classical view of visual attention suggests that there is no competition within the visual field. Within this theory an individual is assumed to be capable of processing all information provided concurrently.
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An analogy to this is the broadcasting region of a radio antenna. In each smaller individual location within the entire area it is possible to access every channel, similar to how the entirety of the information of a hologram is contained within a part. Another analogy of a hologram is the way sunlight illuminates objects in the visual field of an observer. It doesn't matter how narrow the beam of sunlight is.
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Kowler (1995) proposed two models to explain the relationship between attention, saccades and transsaccadic memory. The spatial model, states that attention is distributed among the perceptual site (visual field) and the saccadic target during the latency period, which allows for the identification of the saccadic target and object surrounding that area. The temporal model states that attention determines where the saccade will occur and releases a “go” signal to initiate a saccade within that area.
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He also reported to have grabbed his wife with his left hand and shaken her violently, at which point his right hand came to her aid and grabbed the aggressive left hand. However, such conflicts are very rare. If a conflict arises, one hemisphere usually overrides the other. When split-brain patients are shown an image only in the left half of each eye's visual field, they cannot vocally name what they have seen.
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B3 is a disability sport classification for people who have partial vision. The International Blind Sports Federation (IBSA) defines this classification as "From visual acuity above 2/60 to visual acuity of 6/60 and/or visual field of more than 5 degrees and less than 20 degrees." The Canadian Paralympic Committee defined B3 as "No more than 10% functional vision." Competitors in this class "can make out shapes with the help of glasses".
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Figure 2. Simulation of disparity from depth in the plane. (relates to Figure 1) Brain cells (neurons) in a part of the brain responsible for processing visual information coming from the retinae (primary visual cortex) can detect the existence of disparity in their input from the eyes. Specifically, these neurons will be active, if an object with "their" special disparity lies within the part of the visual field to which they have access (receptive field).
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Frequently patients will have reduced stereopsis, large accommodative lag on dynamic retinoscopy, and a reduced visual field (tubular or spiral field). Streff Syndrome was first described in 1962 by an optometrist, Dr. John Streff as Non-malingering syndrome. In 1962, Dr. Streff and Dr. Richard Apell expanded the concept to add early adaptive syndrome as a precursor to Streff syndrome. Dr. Streff believed the visual changes were induced by stress from reading.
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Vilayanur S. Ramachandran in his research proved that the unconscious brain not only screens certain data from the conscious brain, rendering visual data inaccurate, but also is responsible for filling in false data in place of missing data in certain circumstances. In his paper on "Perceptual filling in of artificially induced scotomas in human vision" he records the effect of the unconscious brain filling in the blind spots in the human visual field.
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At this distance, viewers with better than 20/20 vision will still be able to see the individual pixels. The TV image is composed of many lines of pixels. Ideally, the TV watcher sits far enough away from the screen that the individual lines merge into one solid image. The watcher may sit even farther away and still see a good picture, but it will be a smaller portion of their visual field.
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Showing Rana blob detection. The extent of the blob (a moving bee) is shown by the bounding rectangle in addition to detecting moving blobs, the Rana system can also track the path of these blobs through its visual field. If required be split into a number of sub-fields within which blobs can be tracked independently. This permits a single camera to monitor a number of visual channels reducing system hardware complexity and expense.
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Paris as seen with full visual fields In binasal hemianopsia, vision is missing in the inner (nasal or medial) half of both the right and left visual fields. Information from the nasal visual field falls on the temporal (lateral) retina. Those lateral retinal nerve fibers do not cross in the optic chiasm. Calcification of the internal carotid arteries can impinge the uncrossed, lateral retinal fibers, leading to loss of vision in the nasal field.
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Different people are affected very differently by this disease. The main manifestation is fluid-filled cysts that grow on the brain and can cause damage that varies depending on their location and severity. Symptoms may manifest early in infancy, or may manifest as late as adulthood. Symptoms associated with autosomal dominant porencephaly type I include migraines, hemiplegia or hemiparesis, seizures, cognitive impairment, strokes, dystonia, speech disorders, involuntary muscle spasms, visual field defects, and hydrocephalus.
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For example, neurons implicated in processing a part of the visual field see again in the response amplitude due to shifting focus to that part of the field of vision. Therefore, neurons that are gain modulated can represent multiple types of information. The multi-modal nature of these neurons makes them ideal for specific types of computations, mainly coordinate transformations. This creates the ability to think spatially, the main contributor to physical coordination.
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In order to determine the clarity of a diamond, it is examined under a loupe, which is magnification device that enlarges the visual field 10X. Diamonds are inspected to determine whether there are inclusions on its outside or on the inside. Red diamond clarity is measured like all diamonds on the scale from Flawless to Included. Most red diamonds fall within the range of VS1 – SI2 due to the nature of how they were formed.
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To enable the lateralized presentation of visual stimuli, participants must first be fixated at a centralized location, and must be unable to anticipate whether an upcoming stimulus will be presented to the right or left of fixation. Because the center of the visual field, the fovea, may project bilaterally to both RH and LH,Lindell, A.K. & Nicholls, Mike (2003). Cortical representation of the fovea: Implications for visual half-field research. Cortex, 39,111-117.
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Neuropsychology, 20 (6), 700-707. so any task differences greater than 3ms may represent asymmetries in neural dynamics that are more complex than a single hemisphere's simple dominance for a particular task. Moreover, the divided visual field technique represents a relatively coarse and indirect method for localizing brain regions associated with cognitive function. Other neuroimaging techniques, including fMRI, PET, and EEG, will provide more spatial resolution, and more direct measures of neural activity.
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The SITA algorithm optimizes the determination of perimetry thresholds by continuously estimating what the expected threshold is based on the patient's age and neighboring thresholds. In this manner, it can reduce the time necessary to acquire a visual field by up to 50%, and it decreases patient fatigue and increases reliability. SITA mode is now widely used in many computerized automated perimeters. The testing mode interrupts testing when measurement error is reached.
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An optokinetic drum may be used to study visually induced sopite effects. The optokinetic drum is a rotating instrument in which test subjects are seated facing the wall of the drum. The interior surface of the drum is normally striped; thus, as the drum rotates, the subject's eyes are subject to a moving visual field while the subject remains stationary. The speed of the drum and the duration of the test may be varied.
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Some common tests that measure visual health include visual acuity tests, refraction tests, visual field tests and colour vision tests. Visual acuity tests are the most common tests and they measure the ability to bring details into focus at different distances. Usually this test is conducted by having participants read a map of letters or symbols while one eye is covered. Refraction tests measure the eye's need for glasses or corrective lenses.
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Macular sparing is usually a product of unilateral visual cortex lesions, not optic tract or lateral geniculate nucleus lesions in the thalamus. This can help diagnose whether a patient’s visual field loss is due to cortical damage, or optic tract or thalamic damage. Note that macular sparing does not always occur in patients with visual cortex damage. Patients with macular sparing often retain their ability to perform high resolution visual acuity tasks.
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Lesions at this location result in pure alexia, a deficit in word recognition, while other language abilities remain intact. The visual word form area is activated by reading real words and pseudowords more so than random consonant strings, suggesting that it has adapted to incorporate orthographic regularities in language. It also consistently represents visual words regardless of irrelevant variations, which side of the visual field they're presented on, or whether they're uppercase or lowercase.
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Cambridge, MA: MIT Press The N2pc appears over visual cortex contralateral to the location in space to which subjects are attending; if subjects pay attention to the left side of the visual field, the N2pc appears in the right hemisphere of the brain, and vice versa. This characteristic makes it a useful tool for directly measuring the general direction of a person's attention (either left or right) with fine-grained temporal resolution.
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The component's name, N2pc, abbreviates its characteristics. The component belongs to the family of N2 ERP components, a negative deflection in the ERP waveform at a latency of approximately 200-300 ms following a stimulus. The "pc" stands for "posterior- contralateral", describing the topographic distribution of the component. It appears as a greater negativity at posterior electrode sites contralateral to the attended side of the visual field relative to ipsilateral electrode sites.
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This system processes raw visual and auditory information from cameras and microphones. Kismet's vision system can perform eye detection, motion detection and, albeit controversial, skin-color detection. Whenever Kismet moves its head, it momentarily disables its motion detection system to avoid detecting self-motion. It also uses its stereo cameras to estimate the distance of an object in its visual field, for example to detect threats—large, close objects with a lot of movement.
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For example, the right primary somatosensory cortex receives information from the left limbs, and the right visual cortex receives information from the left visual field. The organization of sensory maps in the cortex reflects that of the corresponding sensing organ, in what is known as a topographic map. Neighboring points in the primary visual cortex, for example, correspond to neighboring points in the retina. This topographic map is called a retinotopic map.
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Coloboma of optic nerve, is a rare defect of the optic nerve that causes moderate to severe visual field defects. Coloboma of the optic nerve is a congenital anomaly of the optic disc in which there is a defect of the inferior aspect of the optic nerve. The issue stems from incomplete closure of the embryonic fissure while in utero. A varying amount of glial tissue typically fills the defect, manifests as a white mass.
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Vision in the affected eye is impaired, the degree of which depends on the size of the defect, and typically affects the visual field more than visual acuity. Additionally, there is an increased risk of serous retinal detachment, manifesting in 1/3 of patients. If retinal detachment does occur, it is usually not correctable and all sight is lost in the affected area of the eye, which may or may not involve the macula.
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From there, the ventral pathway goes through V2 and V4 to areas of the inferior temporal lobe: PIT (posterior inferotemporal), CIT (central inferotemporal), and AIT (anterior inferotemporal). Each visual area contains a full representation of visual space. That is, it contains neurons whose receptive fields together represent the entire visual field. Visual information enters the ventral stream through the primary visual cortex and travels through the rest of the areas in sequence.
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Patients have shown the inability to describe in writing or in speech the stimuli that was shown briefly to the left side. The speaking hemisphere, which in most people is the left hemisphere, would not have awareness of stimulus being shown to the right hemisphere (left visual field), except the left hand was able to point to the correct object. Based on his observations and data, Sperry concluded each hemisphere possessed its own consciousness.
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The Amsler grid, used since 1945, is a grid of horizontal and vertical lines used to monitor a person's central visual field. The grid was developed by Marc Amsler, a Swiss ophthalmologist. It is a diagnostic tool that aids in the detection of visual disturbances caused by changes in the retina, particularly the macula (e.g. macular degeneration, Epiretinal membrane), as well as the optic nerve and the visual pathway to the brain.
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Formal visual field testing by perimetry is recommended, as this would show evidence of optic nerve compression by a tumor. Other tests that may assist in the diagnosis of hypopituitarism, especially if no tumor is found on the MRI scan, are ferritin (elevated in hemochromatosis), angiotensin converting enzyme (ACE) levels (often elevated in sarcoidosis), and human chorionic gonadotropin (often elevated in tumor of germ cell origin). If a genetic cause is suspected, genetic testing may be performed.
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Young children with strabismus normally suppress the visual field of one eye (or part of it), whereas adults who develop strabismus normally do not suppress and therefore suffer from double vision (diplopia). This also means that adults (and older children) have a higher risk of post- operative diplopia after undergoing strabismus surgery than young children. Patients who have undergone strabismus surgery at a young age often have monofixation syndrome (with peripheral binocular fusion and a central suppression scotoma).
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Rapid serial visual presentation (RSVP) is a scientific method for studying the timing of vision. In RSVP, a sequence of stimuli are shown to an observer at one location in their visual field. The observer is instructed to report one of these stimuli - the target - which has a feature that differentiates it from the rest of the stream. For instance, observers may see a sequence of stimuli consisting of grey letters with the exception of one red letter.
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This relationship is also narcissistic. In The Four Fundamental Concepts of Psychoanalysis, Lacan argues that the Symbolic order structures the visual field of the Imaginary, which means that it involves a linguistic dimension. If the signifier is the foundation of the Symbolic, the signified and signification are part of the Imaginary order. Language has Symbolic and Imaginary connotations—in its Imaginary aspect, language is the "wall of language" that inverts and distorts the discourse of the Other.
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The biasing from neural mechanisms guides the search to logical spatial locations (e.g. the table) and items that have similar semantic or visual features to the item that is being searched for. It has been suggested that more than 30 cortical areas in the visual system are used for the processing of visual stimuli, and that there is competition from objects in the visual field that takes place in multiple areas of this extensive network.Desimone R, Ungerleider LG. (1989).
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This theory suggests that the process of visual processing can be biased by other mental processes such as bottom-up and top-down systems which prioritize certain features of an object or whole items for attention and further processing. Biased competition theory is, simply stated, the competition of objects for processing. This competition can be biased, often toward the object that is currently attended in the visual field, or alternatively toward the object most relevant to behavior.
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Visual reorientation is a phenomenon that happens when the perception of an object changes because of the changing visual field and cues. This illusion will alter the astronaut’s perception of the orienting force of gravity and then lose spatial direction. The astronauts must develop good spatial awareness and orientation to overcome visual reorientation. In the traditional disorientation training, for instance, the Yuri Gagarin Cosmonaut Training Center trains the astronaut by simulating a microgravity environment through a centrifuge.
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Fusiform Face Area: The Fusiform Face Area (FFA) is an area that has been studied to be highly active when faces are being attended to in the visual field. A FFA is found to be present in both hemispheres, however, studies have found that the FFA is predominantly lateralized in the right hemisphere where a more in-depth cognitive processing of faces is conducted. The left hemisphere FFA is associated with rapid processing of faces and their features.
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Peli E. (2000) Field Expansion for Homonymous Hemianopia by Optically Induced Peripheral Exotropia, Optometry and Vision Science, Vol. 77, No. 9, September 2000 Development of the lens and clinical trials were funded by NEI-NIH Grant EY014723 awarded to Chadwick Optical. The results of the multi-center clinical trials were published in 2008 reporting a 74% patient acceptance rate.Bowers A, Keeney K, Peli E. (2008) Community-Based Trial of Peripheral Prism Visual Field Expansion Device for Hemianopia.
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Palinopsia is a pathological symptom and should be distinguished from physiological afterimages, a common and benign phenomenon. Physiological afterimages appear when viewing a bright stimulus and shifting visual focus. For example, after staring at a computer screen and looking away, a vague afterimage of the screen remains in the visual field. A stimulus consistently produces the same afterimage, which is dependent on the stimulus intensity and contrast, the time of fixation, and the retinal adaptation state.
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The Glaucoma Hemifield Test (GHT) provides assessment of the visual field where glaucomatous damage is often seen. It compares five corresponding and mirrored areas in the superior and inferior visual fields. The result of either 'Outside Normal Limits' (significant difference in superior and inferior fields), 'Borderline' (suspicious differences) or 'Within Normal Limits' (no differences) is only considered when the patient has, or is a suspect for, glaucoma. This is only available in 30-2 and 24-2 Analyser protocol.
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This stronger motion signal forces us to perceive vertical motion. Functionally, this mechanism has evolved to ensure that we perceive a moving pattern as a rigid surface moving in one direction. Individual motion-sensitive neurons in the visual system have only limited information, as they see only a small portion of the visual field (a situation referred to as the "aperture problem"). In the absence of additional information the visual system prefers the slowest possible motion: i.e.
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Another variant of the basic paradigm of selective attention is the visuospatial cueing paradigm. In this paradigm stimuli are presented one at a time in a fixed number of locations in the visual field. Participants are to look for and indicate if a particular stimulus is the target stimulus. The main aspect of this paradigm is that prior to every presentation of a stimulus there is a cue, indicating where the stimulus is going to be present.
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People with homonymous hemianopsia often experience discomfort in crowds. "A patient with this condition may be unaware of what he or she cannot see and frequently bumps into walls, trips over objects or walks into people on the side where the visual field is missing." Prism Glasses Expand The View For Patients With Hemianopia, Medical News today, 14 May 2008, www.medicalnewstoday.com/articles/107160.php A related phenomenon is hemispatial neglect, the possible neglect of the right or left.
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Carl Benjamin Boyer, The Rainbow: From Myth to Mathematics (1959) The work is also important for the early history of perception. Ptolemy combined the mathematical, philosophical and physiological traditions. He held an extramission-intromission theory of vision: the rays (or flux) from the eye formed a cone, the vertex being within the eye, and the base defining the visual field. The rays were sensitive, and conveyed information back to the observer's intellect about the distance and orientation of surfaces.
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A developed area in attention is the control of visual attention - models that attempt to answer, "where will an individual look next?" A subset of this concerns the question of visual search: How rapidly can a specified object in the visual field be located? This is a common subject of concern for human factors in a variety of domains, with a substantial history in cognitive psychology. This research continues with modern conceptions of salience and salience maps.
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Additional vertical segments on top of horizontal bars significantly decreased prey-catching responses. In general, movement of a rectangle in the direction of its long axis is perceived by the toad to be wormlike, whereas movement along the short axis is interpreted as anti-wormlike. By means of a different experimental setup it was shown that the worm vs. anti-worm discrimination is independent (invariant) of the direction the object moves in the toad's visual field.
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In patients with facial burns, exposure keratopathy, or chronic epiphora, an ophthalmologist may suggest eyelid reconstruction surgery. Depending on the severity of physical trauma sustained, surgical realignment of the extraocular muscles may relieve strabismus. Realignment of the extraocular muscles is also indicated in chronic diplopia that occurs within 20-degrees of the visual field. All patients that have sustained a traumatic brain injury in the absence of ocular trauma are still recommended to obtain examination by an optometrist.
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Visual field of homonymous hemianopia The ophthalmic features of Bonnet–Dechaume–Blanc syndrome occur as retinal arteriovenous malformation (AVMs). There are three categories of AVMs based on their severity. The first category consists of the patient having small lesions that usually are asymptomatic. The second category, more severe than the first, is when the patient's malformation is missing a connecting capillary between an artery and a vein; without it, edema, hemorrhage, and visual impairment can result.
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Perception is linked to specific brain activity and so can be elicited by brain stimulation. The (illusory) percepts that can be evoked range from simple phosphenes (detections of lights in the visual field) to high-level percepts. In a single-case study on a patient undergoing presurgical evaluation for epilepsy treatment, electrical stimulation at the left temporo-parietal junction evoked the percept of a nearby (illusory) person who "closely 'shadowed' changes in the patient's body position and posture".
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Inflammatory markers such ESR, and CRP may be elevated. A complete ophthalmic examination may include a slit lamp examination, optical coherence tomography to detect nerve loss, visual field examinations, fundoscopic examination to assess optic disc atrophy and retinal disease, fundoscopic angiography, and visual evoked potentials, which may demonstrate increased latency. Optic nerve enhancement may be identified on Magnetic Resonance Imaging (MRI) in some patients with acute optic neuropathy. However, a normal study does not rule out optic neuropathy.
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131-140 It is now thought, however, that the illusion of movement in animation is due to the way in which the visual perception areas of our brain map movement in the real world. Our brain is thought to perceive movement by taking individual snapshots of the visual field and inducing that movement has occurred due to the changing position of things.Zeki, S. & Lamb, M, 'The Neurology of Kinetic Art' in Brain. Vol 117. 1994. pp.607-636.
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Ocular hypertension is the presence of elevated fluid pressure inside the eye (intraocular pressure), usually with no optic nerve damage or visual field loss.American Academy of Ophthalmology American Optometric Association - Ocular Hypertension For most individuals, the normal range of intraocular pressure is between 10 mmHg and 21 mmHg.webMD - Tonometry Elevated intraocular pressure is an important risk factor for glaucoma. One study found that topical ocular hypotensive medication delays or prevents the onset of primary open-angle glaucoma.
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The role of retinotopy in other areas, where neurons have large receptive fields, is still being investigated. Location and visuotopic organization of marmoset primary visual cortex (V1) Retinotopy mapping shapes the folding of the cerebral cortex. In both the V1 and V2 areas of macaques and humans the vertical meridian of their visual field tends to be represented on the cerebral cortex's convex gyri folds whereas the horizontal meridian tends to be represented in their concave sulci folds.
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Retinal migraine is associated with transient monocular visual loss (scotoma) in one eye lasting less than one hour. During some episodes, the visual loss may occur with no headache and at other times throbbing headache on the same side of the head as the visual loss may occur, accompanied by severe light sensitivity and/or nausea. Visual loss tends to affect the entire monocular visual field of one eye, not both eyes. After each episode, normal vision returns.
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Palinopsia can occur from posterior visual pathway (post-geniculate) deafferentation, which causes homonymous visual field deficits. This mechanism is thought to be similar to the deafferentation hyperexcitability seen in visual release hallucinations (Charles Bonnet syndrome), which are distinguished from palinopsia by whether the formed image or scene previously occurred. It is hypothesized that deafferentation hyperexcitability is the cause of neuropathic pain. Molecular changes from deafferentation include an increase in presynaptic neurotransmitter vesicles and heightened post-synaptic receptor sensitivity.
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Perhaps the most famous example of an illusory contour is the Pac-Man configuration popularized by Gaetano Kanizsa. Kanizsa figurers trigger the percept of an illusory contour by aligning Pac-Man-shaped inducers in the visual field such that the edges form a shape. Though not explicitly part of the image, Kanizsa figures evoke the percept of a shape, defined by a sharp illusory contour. Typically, the shape seems brighter than the background though luminance is in reality homogeneous.
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Visual agnosia is an impairment in recognition of visually presented objects. It is not due to a deficit in vision (acuity, visual field, and scanning), language, memory, or intellect. While cortical blindness results from lesions to primary visual cortex, visual agnosia is often due to damage to more anterior cortex such as the posterior occipital and/or temporal lobe(s) in the brain.[2] There are two types of visual agnosia: apperceptive agnosia and associative agnosia.
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With the 14 MeV neutron beam, however, LF were reported. Lasting for short periods of time, "streaks" were reported when the beam entered one eye from the front. The "streaks" seen had varying lengths (a maximum of 2 degrees of visual angle), and were seen to either have a blueish-white color or be colorless. All but one observer reported seeing fainter but a higher number of "points" or short lines in the center of visual field.
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Vision may be tested by examining the visual fields, or by examining the retina with an ophthalmoscope, using a process known as funduscopy. Visual field testing may be used to pin-point structural lesions in the optic nerve, or further along the visual pathways. Eye movement is tested and abnormalities such as nystagmus are observed for. The sensation of the face is tested, and patients are asked to perform different facial movements, such as puffing out of the cheeks.
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Apache Guardian set to deploy on May – Koreatimes.co.kr, 26 January 2016 In August 2012, 24 U.S. Army AH-64Ds were equipped with the Ground Fire Acquisition System (GFAS), which detects and targets ground-based weapons fire sources in all-light conditions and with a 120° visual field. The GFAS consists of two sensor pods working with the AH-64's other sensors, and a thermographic camera that precisely locates muzzle flashes.Ground Fire Acquisition System – Armedforces-int.
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Swelling or obstruction of the passage of cerebrospinal fluid (CSF) from the brain may cause (early) signs of increased intracranial pressure which translates clinically into headaches, vomiting, or an altered state of consciousness, and in children changes to the diameter of the skull and bulging of the fontanelles. More complex symptoms such as endocrine dysfunctions should alarm doctors not to exclude brain tumors. A bilateral temporal visual field defect (due to compression of the optic chiasm) or dilation of the pupil, and the occurrence of either slowly evolving or the sudden onset of focal neurologic symptoms, such as cognitive and behavioral impairment (including impaired judgment, memory loss, lack of recognition, spatial orientation disorders), personality or emotional changes, hemiparesis, hypoesthesia, aphasia, ataxia, visual field impairment, impaired sense of smell, impaired hearing, facial paralysis, double vision, or more severe symptoms such as tremors, paralysis on one side of the body hemiplegia, or (epileptic) seizures in a patient with a negative history for epilepsy, should raise the possibility of a brain tumor.
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In light of recent genetic research, the kites of the traditional subfamily Milvinae may also belong to this group. Hawks, including the accipitrines, are believed to have vision several times sharper than humans, in part because of the great number of photoreceptor cells in their retinas (up to 1,000,000 per square mm, against 200,000 for humans), a very high number of nerves connecting the receptors to the brain, and an indented fovea, which magnifies the central portion of the visual field.
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Once a new object is detected, the cells that fire the strongest to stimuli within this specific area of the visual field will fire, causing the eyes to move and focus on this object. Although the superior colliculus may not be directly related to memory for objects across saccades, it is directly related to the control of saccades and selection of fixation targets.Song, J, Rafal, R, & McPeek, R. (2010). Neural substrates of target selection for reaching movements in superior colliculus.
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The patients who display utilization behavior tend to reach out and begin to automatically use objects in the visual field of their environment. This may not seem incorrect but the difference in action to a person without UB is that the "object-appropriate" action taken is performed at the inappropriate time. For example, a patient in a doctor's office sees a toothbrush and will involuntarily start brushing his teeth. This demonstrates the appropriate action (brushing) at the inappropriate time (office).
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This view has been challenged in a review article by Regier and Kay (2009) who discuss a distinction between the questions "1. Do color terms affect color perception?" and "2. Are color categories determined by largely arbitrary linguistic convention?". They report evidence that linguistic categories, stored in the left hemisphere of the brain for most people, do affect categorical perception but primarily in the right-eye visual field, and that this effect is eliminated with a concurrent verbal interference task.
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Aneurysms of the anterior communicating artery are the most common circle of Willis aneurysmBeck J, Rohde S, Berkefeld J, Seifert V, Raabe A. Size and location of ruptured and unruptured intracranial aneurysms measured by 3-dimensional rotational angiography. Surg Neurol. 2006 Jan;65(1):18-25; discussion 25-7. . and can cause visual field defects such as bitemporal heteronymous hemianopsia (due to compression of the optic chiasm),Aoki N. Partially thrombosed aneurysm presenting as the sudden onset of bitemporal hemianopsia. Neurosurgery.
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Glare is typically measured with luminance meters or luminance cameras, both of which are able to determine the luminance of objects within small solid angles. The glare of a scene i.e. visual field of view, is then calculated from the luminance data of that scene. The International Commission on Illumination (CIE) defines glare as: > visual conditions in which there is excessive contrast or an inappropriate > distribution of light sources that disturbs the observer or limits the > ability to distinguish details and objects.
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Visual disturbances are commonly associated with MA, with 97% of patients experiencing visual symptoms. Only 14% of patients with MA experience visual disturbances for more than 60 minutes at a time, with the median duration of visual disturbance being 30 minutes. Typically, visual disturbances in MA patients begin as a zig zag line in the middle of the ocular field which appears to be flickering. Some patients describe symptoms of an expanding red circle in the centre of their visual field.
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Light, no matter how complex its composition of wavelengths, is reduced to three color components by the eye. Each cone type adheres to the principle of univariance, which is that each cone's output is determined by the amount of light that falls on it over all wavelengths. For each location in the visual field, the three types of cones yield three signals based on the extent to which each is stimulated. These amounts of stimulation are sometimes called tristimulus values.
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Pituitary apoplexy is bleeding into or impaired blood supply of the pituitary gland. This usually occurs in the presence of a tumor of the pituitary, although in 80% of cases this has not been diagnosed previously. The most common initial symptom is a sudden headache, often associated with a rapidly worsening visual field defect or double vision caused by compression of nerves surrounding the gland. This is often followed by acute symptoms caused by lack of secretion of essential hormones, predominantly adrenal insufficiency.
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The Cinesphere was renovated while Ontario Place was closed and re-opened on November 3, 2017 with IMAX 70mm and IMAX with laser illumination. During Expo '74 in Spokane, Washington, an IMAX screen that measured was featured in the US Pavilion (the largest structure in the expo). It became the first IMAX Theatre to not be partnered with any other brand of movie theatres. About five million visitors viewed the screen, which covered the viewer's total visual field when looking directly forward.
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In reality it is smaller than this, and irregular, because when the observer is looking straight ahead, his or her nose blocks vision of some possible parts of the surface. In perimetric testing, a section of the imaginary sphere is realized as a hemisphere in the centre of which is a fixation point. Test stimuli can be displayed on the hemisphere. To specify loci in the visual field, a polar coordinate system is used, all expressed from the observer's perspective.
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In bitemporal hemianopsia, vision is missing in the outer (temporal or lateral) half of both the right and left visual fields. Information from the temporal visual field falls on the nasal (medial) retina. The nasal retina is responsible for carrying the information along the optic nerve, and crosses to the other side at the optic chiasm. When there is compression at optic chiasm, the visual impulse from both nasal retina are affected, leading to inability to view the temporal, or peripheral, vision.
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In 1909 was named chief of the entire polyclinic. Reuss made several contributions involving the mathematical aspects of ophthalmic medicine, conducting studies involving optics, ophthalmometry and curvature of the cornea. He also performed extensive research of color blindness, and developed a pseudo-isochromatic color chart that was formerly used to test color blindness.Reuss colour chart at Who Named It He published over 75 scientific works, including a 1902 treatise on the visual field in nervous disorders called Das Gesichtsfeld bei functionellen Nervenleiden.
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According to the biased competition theory, an individual's visual system has limited capacity to process information about multiple objects at any given time. For example, if an individual was presented with two stimuli (objects) and was asked to identify attributes of each object at the same time, the individual's performance would be worse in comparison to if the objects were presented separately. This suggests multiple objects presented simultaneously in the visual field will compete for neural representation due to limited processing resources.
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Vision has been known to play an important role in balance and postural control in humans, along with proprioception and vestibular function. Monocular vision affects how the brain perceives its surroundings by decreasing the available visual field, impairing peripheral vision on one side of the body, and compromising depth perception, all three of which are major contributors to the role of vision in balance.Berela, J. et al. (2011) Use of monocular and binocular visual cues for postural control in children.
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The arrays were therefore presented at 0° (i.e. in line with the participant's trunk midline), at −40° left, and at +40° right. Ultimately, varying the position of the array within the testing visual field allowed for the simultaneous measurement of egocentric neglect and allocentric neglect. The results of this experimental design showed that the spatial neglect patients performed more poorly for the allocentric left side of the triangle, as well as for objects presented on the egocentric left side of the body.
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The integration of these two separately tuned sensors allows the flies to detect a wide range of angular velocities in all three directions of rotation. Two main aspects of the visual field have been used to study fly vision, figure and background. Figures are the objects that the fly is focused on and background represents everything else. When haltere bulbs are removed from tethered flying flies, they are still able to track moving figures, but they struggle to stabilize moving backgrounds.
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In addition, patients may experience difficulty making guiding movements towards objects, and may experience a decline in literacy skills including reading, writing, and spelling. Furthermore, if neural death spreads into other anterior cortical regions, symptoms similar to Alzheimer's disease, such as memory loss, may result. PCA patients with significant atrophy in one hemisphere of the brain may experience hemispatial neglect, the inability to see stimuli on one half of the visual field. Anxiety and depression are also common in PCA patients.
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When trying to map out how corollary discharge works in the brain, it is important to begin with the superior colliculus. It is responsible for receiving visual signals from the retina. In studies done on primate brains, a corollary discharge pathway has been found to begin in the superior colliculus. After receiving current information about the visual field, a corollary discharge signal is sent from the superior colliculus to the frontal eye field, via the medial dorsal nucleus of the thalamus.
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Moving in a straight-line-fashion, microsaccades have the ability to carry the retinal image from several dozen to several hundred photoreceptor widths. Because they shift the retinal image, microsaccades overcome adaption and generate neural responses to stationary stimuli in visual neurons. These movements might serve the function of maintaining visibility during fixation, or might be related to attentional shifts to objects in the visual field or in memory, might help limit binocular fixation disparity, or may serve some combination of those functions.
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Hallucinatory palinopsia describes formed afterimages and scenes that are lifelike, high-resolution, long-lasting, occur anywhere in the visual field, and are unpredictable. Illusory palinopsia are caused by diffuse neuronal pathology such as global alterations in neurotransmitter receptors, while hallucinatory palinopsia is typically caused by focal cortical pathology. The clinical characteristics that separate illusory from hallucinatory palinopsia also help differentiate and assess risk in visual illusions and hallucinations. Complex (formed) visual hallucinations are more worrisome than simple visual hallucinations or visual illusions.
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The blue field entoptic phenomenon is an entoptic phenomenon characterized by the appearance of tiny bright dots (nicknamed blue-sky sprites) moving quickly along squiggly lines in the visual field, especially when looking into bright blue light such as the sky. The dots are short-lived, visible for a second or less, and traveling short distances along seemingly random, curvy paths. Some of them follow the same path as predecessors. The dots may be elongated along the path like tiny worms.
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The results from these studies showed that impairing the visual field of juvenile owls did have a slight effect on their responses to visual cues. However, the longer the owls had visual impairment, the easier it was for them to learn to adapt and correct the error of the auditory cues. It has been hypothesized that because owls are born with these innate neuronal connections, they already understand how to use sound localization without having to develop this technique.Knudsen, E & Mogdans, Joachim. 1992.
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Parkinson's disease is linked with Lewy body dementia for their similar hallucinatory symptoms. The symptoms strike during the evening in any part of the visual field, and are rarely polymodal. The segue into hallucination may begin with illusionsMark Derr (2006) "Marilyn and Me," The New York Times, February 14, 2006 where sensory perception is greatly distorted, but no novel sensory information is present. These typically last for several minutes, during which time the subject may be either conscious and normal or drowsy/inaccessible.
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However, as we can scientifically verify, this is clearly not true of the physiological components of the perceptual process. This also brings up the problem of dualism and its relation to representative realism, concerning the incongruous marriage of the metaphysical and the physical. The new objection to the Homunculus Argument claims that it relies on a naive view of sensation. Because the eyes respond to light rays is no reason for supposing that the visual field requires eyes to see it.
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Research has suggested that the attentional focus is variable in size. Eriksen and St James proposed the ‘zoom-lens’ metaphor, which is an alternative to the spotlight metaphor and takes into account the variable nature of attention. This account likens the distribution of attention to a zoom-lens that can narrow or widen the focus of attention. This supports findings that show attention can be distributed both over a large area of the visual field and also function in a focused mode.
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By moving the image in front of the deviated eye, double vision can be avoided and comfortable binocular vision can be achieved. Other applications include yoked prism where the image is shifted an equal amount in each eye. This is useful when someone has a visual field defect on the same side of each eye. Individuals with nystagmus, Duane's retraction syndrome, 4th Nerve Palsy, and other eye movement disorders experience an improvement in their symptoms when they turn or tilt their head.
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Trajan's Column is an example of a continuous narrative A continuous narrative is a type of narrative that illustrates multiple scenes of a narrative within a single frame. Multiple actions and scenes are portrayed in a single visual field without any dividers. The sequence of events within the narrative is defined through the reuse of the main character or characters. It emphasizes the change in movement and state of the repeating characters as indicators of scene or phase changes in the narrative.
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Birds with eyes on the sides of their heads have a wide visual field, while birds with eyes on the front of their heads, such as owls, have binocular vision and can estimate the depth of field. The avian ear lacks external pinnae but is covered by feathers, although in some birds, such as the Asio, Bubo and Otus owls, these feathers form tufts which resemble ears. The inner ear has a cochlea, but it is not spiral as in mammals.
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It has been posited that lateral connections are too slow and cover too little of the visual field to fully explain surround suppression. Feedback from higher areas may explain the discrepancies seen in mechanism for surround suppression based purely on lateral connections. There is evidence that inactivation of higher order areas results in reduced strength of surround suppression. At least one model of excitatory connections from higher levels has been formed in the effort to more fully explain surround suppression.
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Three main types of experiments provide data that support visual indexing theory. Multiple tracking studies demonstrate that more than one object can be tracked within the visual field simultaneously, subitizing studies suggest the existence of a mechanism that allows small numbers of objects to be efficiently enumerated, and subset selection studies show that certain elements of a visual scene can be processed independently of other items. In all three cases, FINSTs provide an explanation of the phenomenon observed.Pylyshyn, Z.W. (1994).
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A major structural component of the mammalian central nervous system, DHA is the most abundant omega−3 fatty acid in the brain and retina. Brain and retinal function rely on dietary intake of DHA to support a broad range of cell membrane and cell signaling properties, particularly in grey matter and retinal photoreceptor cell outer segments, which are rich in membranes. A systematic review found that DHA had no significant benefits in improving visual field in individuals with retinitis pigmentosa.
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FINSTs operate pre-attentively — that is, before attention is drawn or directed to an object in the visual field. Their primary task is to individuate certain salient features in a scene, conceptually distinguishing these from other stimuli. Under visual indexing theory, FINSTing is a necessary precondition for higher level perceptual processing. Pylyshyn suggests that what FINSTs operate upon in a direct sense is 'feature clusters' on the retina, though a precise set of criteria for FINST allocation has not been defined.
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"The question of how FINSTs are assigned in the first instance remains open, although it seems reasonable that they are assigned primarily in a stimulus-driven manner, perhaps by the activation of locally distinct properties of the stimulus- particularly by new features entering the visual field." FINSTs are subject to resource constraints. Up to around five FINSTs can be allocated at any given time, and these provide the visual system information about the relative locations of FINSTed objects with respect to one another.
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Second, there is a lot of amplification in two stages of classic phototransduction: one pigment will activate many molecules of transducin, and one PDE will cleave many cGMPs. This amplification means that even the absorption of one photon will affect membrane potential and signal to the brain that light is in the visual field. This is the main feature that differentiates rod photoreceptors from cone photoreceptors. Rods are extremely sensitive and have the capacity of registering a single photon of light, unlike cones.
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When the patients were asked what they saw, patients said they only saw the flower and did not see the rabbit. The flower is in the right visual field and the left hemisphere can only see the flower. The left hemisphere dominates the interpretation of the stimulus and since it cannot see the rabbit (only being represented in the right hemisphere), patients do not believe they saw a rabbit. They can, however, still point to the rabbit with their left hand.
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CT scans are relatively insensitive to the presence of cerebral lesions, so other neurological imaging such as PET and MRI may be performed. The presence of seizures and epilepsy may also be assessed through EEG. In addition, motor visual function should be assessed through examination of pupillary reactions, ocular motility, optokinetic nystagmus, slit-lamp examination, visual field examination, visual acuity, stereo vision, bimicroscopic examination, and funduscopic examination. Once the performance of such functions have been assessed, a plan for treatment can follow accordingly.
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Vestibular hypofunction can be a unilateral or bilateral vestibular loss. There are three types of vestibular rehabilitation exercises to reduce symptoms in cases where physical dysfunction cannot be reduced. The category of exercises chosen by a vestibular therapist depends on the problems reported by the patient. The following exercises can be used to treat dizziness with fast movements or exposure to intense visual stimuli, difficulty seeing (appearance of bouncing or jumping visual field) with head movement, and trouble with balance.
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First-order representations are those in which adjacent points of the same hemifield always map to adjacent columns in the contralateral cortex. An example of this would be the map in primary visual cortex (V1). Second-order representations, also known as a field discontinuity map, are maps that are organized such that it appears that a discontinuity has been introduced in either the visual field or the retina. The maps in V2 and other extrastriate cortex are second-order representations.
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The eyes of most frogs are located on either side of the head near the top and project outwards as hemispherical bulges. They provide binocular vision over a field of 100° to the front and a total visual field of almost 360°. They may be the only part of an otherwise submerged frog to protrude from the water. Each eye has closable upper and lower lids and a nictitating membrane which provides further protection, especially when the frog is swimming.
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Aerial casque-butting has also been reported in the great hornbill.Close-up of head of a Malabar grey hornbill showing eyelashesThe plumage of hornbills is typically black, grey, white, or brown, and is frequently offset by bright colours on the bill, or by patches of bare coloured skin on the face or wattles. Some species exhibit sexual dichromatism, where the coloration of soft parts varies by gender. Hornbills possess binocular vision, although unlike most birds with this type of vision, the bill intrudes on their visual field.
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When making an upward saccade, the eyes diverged to be aligned with the most probable uncrossed disparity in that part of the visual field. On the other way around, when making a downward saccade, the eyes converged to enable alignment with crossed disparity in that part of the field. The phenomenon can be interpreted as an adaptation of rapid binocular eye movements to the statistics of the 3D environment, in order to minimize the need for corrective vergence movements at the end of saccades.
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Furthermore, the light seems to change color as it moves across the visual field. A green light will appear to turn red as it seems to move across to the position of a red light. Dennett asks how we could see the light change color before the second light is observed. Velmans argues that the cutaneous rabbit illusion, another illusion that happens in about a second, demonstrates that there is a delay while modelling occurs in the brain and that this delay was discovered by Libet.
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Patient P.S. was a teenage boy in whom it was shown that language comprehension was possible in the right hemisphere. When the word “girlfriend” was flashed to his left visual field, and thus his right hemisphere, he could not verbally say the name of his “crush”, but he then spelled out the name “Liz” with Scrabble tiles. This suggested that even though verbal language was not possible in the right hemisphere, there was a form of language possible through gesturing and left hand movements.
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The eponym Simmonds' syndrome is used infrequently for acquired hypopituitarism, especially when cachexia (general ill health and malnutrition) predominates. Most of the classic causes of hypopituitarism were described in the 20th century; the early 21st century saw the recognition of how common hypopituitarism could be in previous head injury victims. Until the 1950s, the diagnosis of pituitary disease remained based on clinical features and visual field examination, sometimes aided by pneumoencephalography and X-ray tomography. Nevertheless, the field of pituitary surgery developed during this time.
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In visual perception, structure from motion (SFM) refers to how humans recover depth structure from object's motion. The human visual field has an important function: capturing the three-dimensional structures of an object using different kinds of visual cues. SFM is a kind of motion visual cue that uses motion of two-dimensional surfaces to demonstrate three-dimensional objects, and this visual cue works really well even independent of other depth cues. Psychological, especially psychophysical studies have been focused on this topic for decades.
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For example, in one experiment, on each trial, they presented an arithmetic problem in the center of the screen for 1 second, followed by a central cross hair JW was to look at. After 1 more second, Funnell et al. presented a number to one or the other hemisphere/visual field for 150 ms—too fast for JW to move his eyes. Randomly in half the trials, the number was the correct answer; in the other half of the trials it was the incorrect answer.
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IBSA handles classification for a number of sports internationally including five-a-side football, goalball and judo. Part of being classified involves assessing vision for factors including visual acuity, contrast sensitivity, color vision, motion detections and visual field. Assessment into this class by the IBSA involves the athlete filling out a consent form, submitting a photograph, and scheduling an appointment with a classifier for evaluation. During the evaluation, the competitor may be accompanied by another person to assist them in communicating with the classifiers.
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Another example is to observe paintings or photographs of bright, open landscapes that often evoke a feeling of beauty, relaxation, or happiness. This connection to pleasant emotions exists because it was advantageous to humans before today's society to be able to see far into the distance in a brightly lit vista. Similarly, visual images that are dark and/or obscure typically elicit emotions of anxiety and fear. This is because an impeded visual field is disadvantageous for a human to be able to defend itself.
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In 1585 building work stopped, fourteen years after Lanci's death. He also designed the walls of Grosseto in 1564, directing the construction site until his death in 1571, when he was succeeded by his son Marino. Lanci's most notable achievement was his invention in 1567 of a piece of surveying equipment to obtain perspectives with a visual field of 180°. The instrument, which he named distanziometro ("distance meter"), was made of a circular bronze plate placed upon a horizontal tripod the height of which could be adjusted.
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However, the process of visual attention in the deaf is not significantly different from that of hearing subjects. Stronger activations of the auditory cortex during visual observation occur when deaf individuals pay attention to a visual cue, and the activations are weaker if the cue is not in the direct line of sight. One study found that deaf participants process peripheral visual stimuli more quickly than hearing subjects. Deafness appears to heighten spatial attention to the peripheral visual field, but not the central one.
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Since the beginning of his career, Lockhart's research has been focused on identification of injury mechanisms and quantification of sensorimotor deficits and movement disorders associated with aging and neurological disorders on fall accidents. Much of his work has focused on improving the lives of older adults and their families. In the late 1990s, Lockhart studied the biomechanics of slips and falls, how floor surface and visual field obstruction impact falls and how aging affects the likelihood of falls. His research on these topics continued into early 2000s.
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More precisely, the centre of the sphere is in the centre of the pupil of the observer's eye. The observer is looking at a point, the fixation point, on the interior of the sphere. The visual field can be considered to be all parts of the sphere for which the observer can see a particular test stimulus. If we consider this surface to be that on which an observer can see anything, then it is a section of the sphere somewhat larger than a hemisphere.
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Symptoms of Bálint's syndrome were found in the case of a 29-year-old migraine sufferer. In the aura before the migraine headache, she experienced an inability to see all of the objects in the visual field simultaneously; an inability to coordinate hand and eye movements; and an inability to look at an object on command. Symptoms were not present before the onset of the migraine or after it passed. A study of a patient with Corticobasal Ganglionic Degeneration (CGBD) also showed a development of Bálint's syndrome.
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Furthermore, the light seems to change colour as it moves across the visual field. A green light will appear to turn red as it seems to move across to the position of a red light. Dennett asks how we could see the light change colour before the second light is observed. Dennett claims that conventional explanations of the colour change boil down to either Orwellian or Stalinesque hypotheses, which he says are the result of Descartes' continued influence on our vision of the mind.
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Macular degeneration, also known as age-related macular degeneration (AMD or ARMD), is a medical condition which may result in blurred or no vision in the center of the visual field. Early on there are often no symptoms. Over time, however, some people experience a gradual worsening of vision that may affect one or both eyes. While it does not result in complete blindness, loss of central vision can make it hard to recognize faces, drive, read, or perform other activities of daily life.
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Very few affected individuals go completely blind from retinoschisis, but some sufferers have very limited reading vision and are "legally blind". Visual acuity can be reduced to less than 20/200 in both eyes. Individuals affected by XLRS are at an increased risk for retinal detachment and eye hemorrhage, among other potential complications. Retinoschisis causes acuity loss in the center of the visual field through the formation of tiny cysts in the retina, often forming a "spoke-wheel" pattern that can be very subtle.
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A 23-year-old college student who collapsed the day after a party due to the consumption of heroin showed signs of arterial branch disease in the interior, middle and left parietal veins through bilateral carotid angiography. Further testing, radio isotope scintigraphy, revealed the spread of a left parietal occipital tumor a week after. Once fully conscious, the patient showed signs of hemiparesis and deficit in right visual field. However, the patient was still able to speak with no sign of disturbance in language.
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PRES usually has an acute onset. Most people with PRES experience headaches and seizures; many also experience visual changes, confusion and drowsiness, weakness of the arm and/or leg on one side of the body (hemiplegia), difficulty speaking, or more rarely other neurological symptoms. The visual changes in PRES may include hemianopsia (inability to see the left or right part of the visual field), blurred vision, lack of visual awareness on one side, visual hallucinations, and cortical blindness. Seizures occur in about two thirds of cases.
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A 2013 Cochrane Systematic Review compared the effect of brimonidine and timolol in slowing the progression of open angle glaucoma in adult participants. The results showed that participants assigned to brimonidine showed less visual field progression than those assigned to timolol, though the results were not significant, given the heavy loss-to-followup and limited evidence. The mean intraocular pressures for both groups were similar. Participants in the brimonidine group had a higher occurrence of side effects caused by medication than participants in the timolol group.
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MedDraw is a computer-based drawing-task diagnosis and rehabilitation system project between the University of Kent, UK and the University of Rouen, France, coordinated by Dr. Richard Guest and started in 2003. The project aims to develop a robust, state-of-the art, yet easy to use clinical system producing objective diagnostic recommendations across a range of clinical conditions. Their focus is to detect spatial neglect in the visual field and organization of movement disorder. They will remain focused on drawing-based diagnosis of these disorders.
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Lesions in the visual pathway affect vision most often by creating deficits or negative phenomena, such as blindness, visual field deficits or scotomas, decreased visual acuity and color blindness. On occasion, they may also create false visual images, called positive visual phenomena. These images can be a result of distortion of incoming sensory information leading to an incorrect perception of a real image called an illusion. When the visual system produces images which are not based on sensory input, they can be referred to as hallucinations.
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To perceive depth, infants as well as adults rely on several signals such as distances and kinetics. For instance, the fact that objects closer to the observer fill more space in our visual field than farther objects provides some cues into depth perception for infants. Evidence has shown that newborns' eyes do not work in the same fashion as older children or adults – mainly due to poor coordination of the eyes. Newborn's eyes move in the same direction only about half of the time.
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The presence of monocular ambient occlusions consist of the object's texture and geometry. These phenomena are able to reduce the depth perception latency both in natural and artificial stimuli. ; Curvilinear perspective : At the outer extremes of the visual field, parallel lines become curved, as in a photo taken through a fisheye lens. This effect, although it is usually eliminated from both art and photos by the cropping or framing of a picture, greatly enhances the viewer's sense of being positioned within a real, three- dimensional space.
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Autostereograms take advantage of this process in order to trick the brain to form an apparent Cyclopean image from seemingly random patterns. These random patterns appear often in daily life such as in art, children's books, and architecture. Cyclopean image is named after the mythical being, Cyclops, a creature possessing one single eye. The single refers to the way stereo sighted viewers perceive the center of their fused visual field as lying between the two physical eyes, as if seen by a cyclopean eye.
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This led Sperry to believe that only the left side of the brain could articulate speech. However, in a follow-up experiment, Sperry discovered that the right hemisphere does have some language abilities. In this experiment, he had the patients place their left hands in a tray full of objects located under a partition so the patient would not be able to see the objects. Then a word was shown to the patient's left visual field, which was processed by the right side of the brain.
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The P2 has also been found to be involved in language processes including sentential constraint and expectancy for a given word. Researchers found that the P2 component varied with the level of expectancy for a particular item in a sentence for right but not left visual field presentations, suggesting that the left hemisphere of the brain may use contextual information to prepare for the visual analysis of upcoming stimuli.Federmeier, K. D., & Kutas, M. (2002). Picture the difference: electrophysiological investigations of picture processing in the two cerebral hemispheres.
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A number of experiments have reproduced this effect in animal subjects. Still other experiments have explored nature of stimulus factors that affect the speed and accuracy of visual search. For example, the time taken to find a single target increases as the number of items in the visual field increases. This rise in RT is steep if the distracters are similar to the target, less steep if they are dissimilar, and may not occur if the distracters are very different from the target in form or color.
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The nature of prey selection by two centrarchids (white crappie and bluegill) has been presented as a model incorporating optimal foraging strategies by Manatunge & Asaeda . The visual field of the foraging fish as represented by the reactive distance was analysed in detail to estimate the number of prey encounters per search bout. The predicted reactive distances were compared with experimental data. The energetic cost associated with fish foraging behaviour was calculated based on the sequence of events that takes place for each prey consumed.
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At any moment, the LUI displays a small region of the overall graph, and the scene is automatically arranged in real time so as to provide good visibility for all of the Items present. An overall visual context is created which allows items to adopt fixed visual reference locations, one relative to one another, and which fosters the visual articulation and mapping of the visual field. LUIs are designed to operate as context interfaces, and inherently provide distinct and notionally fixed visual reference locations for data items.
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An optokinetic drum —also called catford drum— is a rotating instrument to test vision in which individuals are seated facing the wall of the drum. The interior surface of the drum is normally striped; thus, as the drum rotates, the subject's eyes are subject to a moving visual field while the subject remains stationary, this phenomenon is called optokinetic Nystagmus. The speed of the drum and the duration of the test may be varied. Control groups are placed in a drum without stripes or rotation.
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Cerebral polyopia is sometimes confused with palinopsia (visual trailing), in which multiple images appear while watching an object. However, in cerebral polyopia, the duplicated images are of a stationary object which are perceived even after the object is removed from the visual field. Movement of the original object causes all of the duplicated images to move, or the polyopic images disappear during motion. In palinoptic polyopia, movement causes each polyopic image to leave an image in its wake, creating hundreds of persistent images (entomopia).
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Amacrine cells and other retinal interneuron cells are less likely to be near neighbours of the same subtype than would occur by chance, resulting in 'exclusion zones' that separate them. Mosaic arrangements provide a mechanism to distribute each cell type evenly across the retina, ensuring that all parts of the visual field have access to a full set of processing elements. MEGF10 and MEGF11 transmembrane proteins have critical roles in the formation of the mosaics by starburst amacrine cells and horizontal cells in mice.
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A visual field test can differentiate between whether the reduced visual acuity is centered on the optic nerve or the fundus. Once a neurological problem has, therefore, been ruled out, the disorder's reduced visual acuity without visible fundus abnormalities may be misdiagnosed as optic neuritis, dominant optic atrophy, amblyopia, or nonorganic visual disorder. The combination of weak amplitudes in the mfERG with no visible fundus abnormalities then rules out other explanations. For example, OMD presents negative for a full-field ERG while retinitis pigmentosa presents abnormal.
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In 1918, Goldstein and Gelb reported a 24-year-old male who suffered a gunshot wound in the posterior brain. The patient reported no impression of movement. He could state the new position of the object (left, right, up, down), but saw "nothing in between". While Goldestein and Gelb believed the patient had damaged the lateral and medial parts of the left occipital lobe, it was later indicated that both occipital lobes were probably affected, due to the bilateral, concentric loss of his visual field.
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CN IV). The symptoms occur in this order because the parasympathetic fibers surround the motor fibers of CN III and are hence compressed first. Compression of the ipsilateral posterior cerebral artery will result in ischemia of the ipsilateral primary visual cortex and contralateral visual field deficits in both eyes (contralateral homonymous hemianopsia). Another important finding is a false localizing sign, the so-called Kernohan's notch, which results from compression of the contralateralRobins Basic Pathology cerebral crus containing descending corticospinal and some corticobulbar tract fibers.
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Dextromethorphan gel capsules Over-the-counter preparations containing dextromethorphan have been used in manners inconsistent with their labeling, often as a recreational drug. At doses much higher than medically recommended, dextromethorphan and its major metabolite, dextrorphan, acts as an NMDA receptor antagonist, which produces dissociative hallucinogenic states somewhat similar to ketamine and phencyclidine. It may produce distortions of the visual field – feelings of dissociation, distorted bodily perception, excitement, and a loss of sense of time. Some users report stimulant-like euphoria, particularly in response to music.
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Humphrey describes his book as "a partial history of a part of what constitutes the human mind: an evolutionary history of how sensory consciousness has come into the world and what it is doing there." He discusses the views of the poet Samuel Taylor Coleridge and the philosophers Colin McGinn and Daniel Dennett, and the phenomenon known as blindsight, in which people who are blind in a large part of the visual field nevertheless retain "certain perceptual faculties" and apparently have "perception without sensation".
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RP begins with death of rod photoreceptor cells, which are the only cells in the retina to express rhodopsin and which express it as their most abundant protein. Eventually, loss of rod cells leads to loss of cone cells (cone photoreceptors), the mainstay of human vision. Symptoms of RP include loss of sensitivity to dim light, abnormal visual function, and characteristic bone spicule deposits of pigment in the retina. Affected individuals progressively lose visual field and visual acuity, and photoreceptor cell death can ultimately lead to blindness.
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The IT cortex in humans is also known as the Inferior Temporal Gyrus since it has been located to a specific region of the human temporal lobe. The IT processes visual stimuli of objects in our field of vision, and is involved with memory and memory recall to identify that object; it is involved with the processing and perception created by visual stimuli amplified in the V1, V2, V3, and V4 regions of the occipital lobe. This region processes the color and form of the object in the visual field and is responsible for producing the “what” from this visual stimuli, or in other words identifying the object based on the color and form of the object and comparing that processed information to stored memories of objects to identify that object. The IT cortex’s neurological significance is not just its contribution to the processing of visual stimuli in object recognition but also has been found to be a vital area with regards to simple processing of the visual field, difficulties with perceptual tasks and spatial awareness, and the location of unique single cells that possibly explain the IT cortex’s relation to memory.
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The main symptoms of Devic's disease are loss of vision and spinal cord function. Optic neuritis may manifest as visual impairment with decreased visual acuity, although visual field defects, or loss of color vision may occur in isolation or prior to formal loss of acuity. Spinal cord dysfunction can lead to muscle weakness, reduced sensation, or loss of bladder and bowel control. The typical patient has an acute and severe spastic weakness of the legs (paraparesis) or all four limbs (quadriparesis) with sensory signs, often accompanied by loss of bladder control.
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A neural structure located behind the lateral geniculate nucleus that is understood to control eye movements. In particular, the deeper layers of the superior colliculus, known as lamina VI and VII, have been found to be involved in initiating and executing saccadic eye movements, which includes the desired speed and direction of the saccade.Quessy, S, Quinet, J, & Freedman, G. (2010) The cells in these layers are organized in a way that forms a map of the visual field. They are organized according to what direction each cell moves the eye.
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This method of hunting is commonly applied to lizards or snakes. An adult male trained to strike at a rubber snake on a force plate was found to hit with a force equal to five times its own body weight, with a contact period of only 10–15 milliseconds. This short time of contact suggests that the secretarybird relies on superior visual targeting to determine the precise location of the prey's head. Although little is known about its visual field, it is assumed that it is large, frontal and binocular.
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There simply are not enough cone cells away from the center of the visual field to identify words in the periphery of the field. It has been suggested that the fixation span can be stretched through training (meta guiding) to take in as much as a line for the purpose of skimming or speed reading. However other sources suggest that using this method can result in a severely reduced comprehension rate in comparison to normal reading ("rauding"). Some speed reading courses stress that the human eye has to move very quickly.
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In recent years, researchers have successfully developed experimental brain–computer interfaces or neuroprostheses that stimulate phosphenes to restore vision to people blinded through accidents. Notable successes include the human experiments by William H. Dobelle and Mark Humayun and animal research by Dick Normann. A noninvasive technique that uses electrodes on the scalp, transcranial magnetic stimulation, has also been shown to produce phosphenes. Experiments with humans have shown that when the visual cortex is stimulated above the calcarine fissure, phosphenes are produced in the lower part of the visual field, and vice versa.
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Water absorbs light of long wavelengths, so less light from these wavelengths reflects back to reach the eye. Therefore, warm colors from the visual light spectrum appear less vibrant at increasing depths. Water scatters light of shorter wavelengths above violet, meaning cooler colors dominate the visual field in the photic zone. Light intensity decreases 10 fold with every 75 m of depth, so at depths of 75 m, light is 10% as intense as it is on the surface, and is only 1% as intense at 150 m as it is on the surface.
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Thus any type of fluorescence depends on the presence of external sources of light. Biologically functional fluorescence is found in the photic zone, where there is not only enough light to cause fluorescence, but enough light for other organisms to detect it. The visual field in the photic zone is naturally blue, so colors of fluorescence can be detected as bright reds, oranges, yellows, and greens. Green is the most commonly found color in the marine spectrum, yellow the second most, orange the third, and red is the rarest.
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Figure 2 Transformations of the visual field toward the visual map on the primary visual cortex in vertebrates. U=up; D=down; L=left; R=right; F=fovea For the different types of optic chiasm, see In all vertebrates, the optic nerves of the left and the right eye meet in the body midline, ventral to the brain. In many vertebrates the left optic nerve crosses over the right one without fusing with it. In vertebrates with a large overlap of the visual fields of the two eyes, i.e.
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The inferonasal retina are related to the anterior portion of the optic chiasm whereas superonasal retinal fibers are related to the posterior portion of the optic chiasm. The partial crossing over of optic nerve fibres at the optic chiasm allows the visual cortex to receive the same hemispheric visual field from both eyes. Superimposing and processing these monocular visual signals allow the visual cortex to generate binocular and stereoscopic vision. The net result is that the right cerebral hemisphere processes left visual hemifield, and the left cerebral hemisphere processes the right visual hemifield.
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When the experimenters conducted the test again, they asked the subjects to point to the lights that lit up. Although subjects had only reported seeing the lights flash on the right, they actually pointed to all the lights in both visual fields. This showed that both brain hemispheres had seen the lights and were equally competent in visual perception. The subjects did not say they saw the lights when they flashed in the left visual field even though they did see them because the center for speech is located in the brain’s left hemisphere.
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Britain's Jade Etherington is a B2 classified Paralympic athlete B2 is a medical based Paralympic classification for blind sport. Competitors in this classification have vision that falls between the B1 and B3 classes. The International Blind Sports Federation (IBSA) defines this classification as "visual acuity ranging from LogMAR 1.50 to 2.60 (inclusive) and/or visual field constricted to a diameter of less than 10 degrees." It is used by a number of blind sports including para-alpine skiing, para-Nordic skiing, blind cricket, blind golf, five-a-side football, goalball and judo.
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IBSA handles classification for a number of sports internationally including five-a-side football, goalball and judo. Part of being classified involves assessing vision for factors including visual acuity, contrast sensitivity, color vision, motion detections and visual field. When being assessed into this class by the IBSA, the process first includes the athlete filling out a consent form, submitting a photograph, and scheduling an appointment with a classifier for evaluation. During the actual evaluation, the competitor may be accompanied by another person to assist them in communicating with the classifiers.
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For adaptive rowing, the comparable classification is LTA-B3; for athletics, the class is T13; and equivalent for swimming is S13. IBSA handles classification for a number of sports internationally including five-a-side football, goalball and judo. Part of being classified involves assessing vision for factors including visual acuity, contrast sensitivity, color vision, motion detections and visual field. When being assessed into this class by the IBSA, the process first includes the athlete filling out a consent form, submitting a photograph, and scheduling an appointment with a classifier for evaluation.
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Only on an astronomical scale are physical space and its contents interdependent, This major proposition of the general theory of relativity is of no concern in vision. For us, distances in object space are independent of the nature of the objects. But this is not so simple in visual space. At a minim an observer judges the relative location of a few light points in an otherwise dark visual field, a simplistic extension from object space that enabled Luneburg to make some statements about the geometry of visual space.
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The majority of cases in the 2005 study were the result of bilateral lesions in the ventral occipital cortex. It is unknown whether this was the result of bilateral lesions being more likely to produce color-loss symptoms, or if it was a sampling effect of patients with more severe brain trauma more often being admitted for treatment. In many of the cases examined, patients reported only partial loss of color vision. The locations of color vision loss can be restricted to one hemisphere or one quarter of the visual field.
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Reports also suggest that her memory was so vivid that she could obscure other parts of the present visual field with these past memories. However, this subject remains the only person to have passed such a test, and the credibility of the findings are highly questionable, given that the researcher married his subject, and the tests have never been repeated. The study fueled strong skepticism about studies of eidetic memory for several decades thereafter. Recently there has been a renewal of interest in the area, with more careful controls, and far less spectacular results.
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Astronauts are also affected by this region, which is said to be the cause of peculiar "shooting stars" (phosphenes) seen in the visual field of astronauts, an effect termed cosmic ray visual phenomena. Passing through the South Atlantic Anomaly is thought to be the reason for the failures of the Globalstar network's satellites in 2007. The PAMELA experiment, while passing through the SAA, detected positron levels that were orders of magnitude higher than expected. This suggests the Van Allen belt confines antiparticles produced by the interaction of the Earth's upper atmosphere with cosmic rays.
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Once the optic nerve is damaged, it is more likely to incur more damage, and if severe visual loss is present, there is greater impact on the patient from any additional damage that may occur. An initial reduction in the intraocular pressure of 20% from baseline is suggested. However, reduction of IOP to the target pressure range does not guarantee that progression will not occur. Therefore, the target pressure range needs to be constantly reassessed and changed as dictated by IOP fluctuations, optic nerve changes, and/or visual field progression.
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Surgery is most likely to improve vision if there was some remaining vision before surgery, and if surgery is undertaken within a week of the onset of symptoms. Those with relatively mild visual field loss or double vision only may be managed conservatively, with close observation of the level of consciousness, visual fields, and results of routine blood tests. If there is any deterioration, or expected spontaneous improvement does not occur, surgical intervention may still be indicated. If the apoplexy occurred in a prolactin-secreting tumor, this may respond to dopamine agonist treatment.
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These observations suggest that the vulture might be regular facultative predators. However, extensive field reports are lacking therefore further research is warranted. Additionally, the visual field of this vulture species is more similar to other predatory species such as the accipitrid hawk than to that of more closely related, carrion feeding Gyps vultures. Specifically, they have a significantly wider binocular field (30°, compared to the 20° of Gyps vultures), which is thought to help with the accurate placement and timing of the talons necessary to capture live prey.
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Head of alt=Head of a mantis with large compound eyes and labrum Mantises have stereo vision. They locate their prey by sight; their compound eyes contain up to 10,000 ommatidia. A small area at the front called the fovea has greater visual acuity than the rest of the eye, and can produce the high resolution necessary to examine potential prey. The peripheral ommatidia are concerned with perceiving motion; when a moving object is noticed, the head is rapidly rotated to bring the object into the visual field of the fovea.
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French said that at least some reports of NDEs might be based upon false memories. According to Engmann (2008) near-death experiences of people who are clinically dead are psychopathological symptoms caused by a severe malfunction of the brain resulting from the cessation of cerebral blood circulation. An important question is whether it is possible to "translate" the bloomy experiences of the reanimated survivors into psychopathologically basic phenomena, e.g., acoasms (nonverbal auditory hallucinations), central narrowing of the visual field, autoscopia, visual hallucinations, activation of limbic and memory structures according to Moody's stages.
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In the late 1960s, people in the Grassy Narrows and Whitedog First Nations populations started to suffer symptoms of mercury poisoning. Several Japanese doctors who had been involved in studying Minamata disease in Japan travelled to Canada to investigate the mercury poisoning in these people. Blood mercury levels were above 100 ppb in a significant number of individuals and above 200 ppb in several others. Symptoms included sensory disturbances, such as narrowing of the visual field, and impaired hearing, abnormal eye movements, tremor, ataxia (impaired balance), and dysarthria (poor articulation of speech).
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For example, this bias can be towards an object which is currently attended to in the visual field or RF, or towards the object that is most relevant to one's behavior. Functional magnetic resonance imaging (fMRI) has shown that biased competition theory can explain the observed attention effects at a neuronal level. Attention effects bias the internal weight (strengthens connections) of task relevant features toward the attended object. This was shown by Reddy, Kanwisher, and van Rullen who found an increase in oxygenated blood to a specific neuron following a locational cue.
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Bálint's syndrome is an uncommon and incompletely understood triad of severe neuropsychological impairments: inability to perceive the visual field as a whole (simultanagnosia), difficulty in fixating the eyes (oculomotor apraxia), and inability to move the hand to a specific object by using vision (optic ataxia). It was named in 1909 for the Austro-Hungarian neurologist and psychiatrist Rezső Bálint who first identified it. Bálint's syndrome occurs most often with an acute onset as a consequence of two or more strokes at more or less the same place in each hemisphere. Therefore, it occurs rarely.
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Simultanagnosia is the inability to perceive simultaneous events or objects in one's visual field. Victims of Bálint's syndrome perceive the world erratically, as a series of single objects rather than seeing the wholeness of a scene. This spatial disorder of visual attention—the ability to identify local elements of a scene, but not the global whole—has been referred to as a constriction of the individual's global gestalt window—their visual "window" of attention. People fixate their eyes to specific images in social scenes because they are informative to the meaning of the scene.
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Probably the most common, widely recognised psychedelic experiential phenomenon is the alteration in visual perception; this includes surfaces in the environment appearing to ripple and undulate. Psychedelic visual alteration also includes spontaneous formation of complex flowing geometric visual patterning in the visual field. When the eyes are open, the visual alteration is overlaid onto the objects and spaces in the physical environment; when the eyes are closed the visual alteration is seen in the "inner world" behind the eyelids. These visual effects increase in complexity with higher dosages, and also when the eyes are closed.
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The "bead", which is a small, spherical device attached to the barrel, acts as a reference. Not to be consciously considered, it comprises a reference allowing the shooter to use their natural instincts to make the shot In the tactical environment, where targets aren't moving across the visual field as quickly, sights do have a role. For many, a fiber-optic front sight is the preferred sighting reference in conjunction with a rear leaf. In this instance, the shotgun is used more like a rifle, allowing intentionally aimed shots.
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Like many other deep-sea fish, their eyes are telescopic, allowing them to see in near darkness. However, unlike any other fishes, their eyes also possess a "pearl organ"; a white spot on the surface of the eye that may help to pick up light from the side of the fish, out of the normal visual field. The pearl organ is associated with a secondary retina, allowing the fish an unusually wide field of view. Pearleyes typically live between , although some species may visit shallower waters during the night.
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Diagnosis of PIC can be difficult because the appearance may be similar to other conditions and types of posterior uveitis, especially other forms of the so-called white dot syndromes. The diagnosis is made by eliminating all the other possibilities by careful examination by an experienced ophthalmologist, aided with visual field testing and Fluorescein angiography (an intravenous dye used to show the blood vessels at the back of the eye). It is important that the correct diagnosis is made because treatment may be quite different for apparently similar conditions.
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In spoken languages, joint attention involves the caregiver speaking about the object that the child is looking at. Deaf signing parents capitalize on moments of joint attention to provide language input. Deaf signing children learn to adjust their eye gaze to look back and forth between the object and the caregiver’s signing. To reduce the child's need for divided attention between an object and the caregiver's signing, a caregiver can position themselves and objects within the child's visual field so that language and the object can be seen at the same time.
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In the late 1800s, Hermann Helmholtz, a German physician and physicist, extensively researched conscious sensations and different types of perception. He defined sensations as the "raw elements" of conscious experience that required no learning, and perceptions as the meaningful interpretations derived from the senses. He studied the physical properties of the eye and vision, as well as acoustic sensation. In one of his classic experiments regarding how space perception could be altered by experience, participants wore glasses that distorted the visual field by several degrees to the right.
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Flies are also able to perform compensatory head movements to stabilize their vision without the use of their halteres. When the visual field is artificially rotated around a fly at slower angular velocities, head stabilization still occurs. Head stabilization outputs due to optical inputs alone are slower to respond, but also last longer than those due to haltere inputs. From this result it can be concluded that although halteres are required for detecting fast rotations, the visual system is adept by itself at sensing and correcting for slower body movements.
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In a PHP test, the macula (central area of the retina) is scanned with a succession of stimuli, each stimulus consisting of a series of dots arranged along a vertical or horizontal axis. In each stimulus, a small number of dots are misaligned, thereby creating an artificial distortion (bump or wave). The examinee's task is to perceive these artificial distortions and mark their locations on the visual field. When a stimulus is projected on a healthy portion of the retina, the examinee identifies the artificial distortion and is likely to mark a correct location.
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The effects of the prism adaptation paradigm are observed when the performance on the perceptual motor task of the pre-and post-test are compared. # Pre-test: For example, the pre-test measures the observer's ability to point to the visual target directly in front of them before prism exposure. This task can be completed with ease and accuracy by normal, healthy individuals. # Prism Exposure: During prism exposure, the initial attempts at pointing to the target are off- target because the observer's visual field has been laterally shifted in one direction.
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Seizures often begin when patients are young, although studies have shown adult onset as well. Many causes of the epilepsy have been theorized, with EEG often finding the hamartoma itself as the source of electrical activity, or epileptogenic focus. With chronic seizures, cognitive decline can develop, which can manifest as poor school performance, decreased nervous stimulus IQ, or limited socialization. Other symptoms of this tumor type include visual disturbances, such as the appearance of motion from a stationary object, or inappropriate color perception of the entire visual field.
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Dejerine in 1892 described specific symptoms resulting from a lesion to the corpus callosum that caused alexia without agraphia. The patient had a lesion in the left occipital lobe, blocking sight in the right visual field (hemianopia), and in the splenium of the corpus callosum. Dejerine interpreted this case as a disconnection of the speech area in the left hemisphere from the right visual cortex. In 1965, Norman Geschwind, an American neurologist, wrote ‘Disconnexion syndromes in animals and man’ where he described a disconnectionist framework that revolutionized neurosciences and clinical neurology.
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The H1 neuron is located in the visual cortex of true flies of the order Diptera and mediates motor responses to visual stimuli. H1 is sensitive to horizontal motion in the visual field and enables the fly to rapidly and accurately respond to optic flow with motor corrections to stabilize flight. It is particularly responsive to horizontal forward motion associated with movement of the fly’s own body during flight. Damage to H1 impairs the fly’s ability to counteract disturbances during flight, suggesting that it is a necessary component of the optomotor response.
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Haidinger saw it when he looked through a mineral that polarized light. Many people are able to perceive polarization of light. Haidinger's brushes, as they are now known, may be seen as a yellowish horizontal bar or bow-tie shape (with "fuzzy" ends, hence the name "brush") visible in the center of the visual field against the blue sky viewed while facing away from the sun, or on any bright background. It typically occupies roughly 3–5 degrees of vision, about twice or three times the width of one's thumb held at arm's length.
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Inputs to the claustrum are organized by modality, which include visual, auditory and somatomotor processing areas. In the same way that the morphology of neurons in the spinal cord is indicative of function (i.e. rexed laminae), the visual, auditory and somatomotor regions within the claustrum share similar neurons with specific functional characteristics. For example, the portion of the claustrum that processes visual information (primarily synthesizing afferent fibers concerned with our peripheral visual field) is comprised by a majority of binocular cells that have “elongated receptive fields and no orientation selectivity.
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Extinction is a phenomenon observable during double simultaneous stimulation of both left and right visual fields. Patients with extinction will fail to perceive the stimulus in the contralesional visual field when presented in conjunction with a stimulus in the ipsilesional field. However, when presented on its own, patients can correctly perceive the contralesional stimulus. Thus, patients with neglect fail to report stimuli present in the aberrant field, whereas patients with extinction fail to report stimuli in the aberrant field only when double simultaneous presentations occur in both hemifields.
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Analogous to neglect, extinction affects the contralesional visuospatial field in majority of patients with unilateral damage. Anatomical correlates of visuospatial neglect and extinction do not overlap absolutely, with extinction proposed to be associated with subcortical lesions. A common method in quick detection of visuospatial extinction is a Finger Confrontation Model. Utilized as standard bedside evaluation, the task requires the patient to indicate (either verbally or by pointing) in which visual field the doctor's hand or finger is moving, while the doctor makes a wiggling motion with his index.
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This in turn blocks the flow of fluids in the eye, leading to a painful increase in intra-ocular pressure (glaucoma) and often irreparable optic nerve damage, leading to visual field loss and eventual blindness. As of November 2011, the Kennel Club has not highlighted any specific concerns regarding the breed's health to conformation show judges. Due to the low numbers of the breed, two of the most prevalent problems facing the breed today is the popular sire effect and the general problem of genetic diversity within the breed.
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Hawks, like most birds, are tetrachromats having four types of colour receptors in the eye. These give hawks the ability to perceive not only the visible range but also ultraviolet light. Other adaptations allow for the detection of polarised light or magnetic fields. This is due to the large number of photoreceptors in the retina (up to 1,000,000 per square mm in Buteo, compared to 200,000 in humans), a high number of nerves connecting these receptors to the brain, and an indented fovea, which magnifies the central portion of the visual field.
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For example, a person who has a lesion of the right optic tract will no longer see objects on his left side. Similarly, a person who has a stroke to the right occipital lobe will have the same visual field defect, usually more congruent between the two eyes, and there may be macular sparing. A stroke on the right side of the brain (especially parietal lobe), in addition to producing a homonymous hemianopsia, may also lead to the syndrome of hemispatial neglect. Transient homonymous hemianopsia does not necessarily mean stroke.
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Electrical stimulation experiments demonstrated that the tectum initiates orienting and snapping behaviors. It contains many different visually sensitive neurons, among these Type I and Type II neurons (later named T5.1 and T5.2, respectively). Type I neurons are activated when an object traversing the toad's visual field is extended in the direction of movement; Type II neurons, too, but they will fire less when the object is extended in a direction that is perpendicular to the direction of movement. Those T5.2 neurons display prey-selective properties; see prey feature detectors.
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Glaucoma in a dog Canine glaucoma refers to a group of diseases in dogs that affect the optic nerve and involve a loss of retinal ganglion cells in a characteristic pattern. An intraocular pressure greater than is a significant risk factor for the development of glaucoma. Untreated glaucoma in dogs leads to permanent damage of the optic nerve and resultant visual field loss, which can progress to blindness. The group of multifactorial diseases which cause glaucoma in dogs can be divided roughly into three main categories: congenital, primary or secondary.
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Boston: Butterworths; 1987. 47-81. They are usually frequent and diurnal, develop rapidly within seconds and are brief, lasting from a few seconds to 1–3 min, and, rarely, longer. Elementary visual hallucinations are the most common and characteristic ictal symptoms, and are most likely to be the first and often the only clinical manifestation. They consist mainly of small multicoloured circular patterns that often appear in the periphery of a visual field, becoming larger and multiplying during the course of the seizure, frequently moving horizontally towards the other side.
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The eyes of M. religiosa are apposition eyes with eight types of photoreceptor cells, so are best adapted for daylight vision. One compound eye of an adult mantid consists of 8,000 to 10,000 optically isolated ommatidia with an interommatidial angle of 2° in the periphery and 0.7° in the fovea. Interommatidial angles in insects vary from tens of degrees to 0.24° in dragonflies, which puts the mantids on the upper end of spatial resolution. The overlap of the visual field of the two eyes is 40° in nymphs and up to 70° in adults.
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While they already have all the necessary structures, very young animals have a restricted visual field and lower resolution and sensitivity to light. The great improvement of vision after only three days happens due to the sclerotisation of the cuticle that includes the corneal lenses of the ommatidia. The improved lenses are not able to focus the light on the retina. Few remarkable new findings have happened concerning the visual system of different mantid species, such as Sphodromantis lineola; using three- dimensional glasses and a 3D-cinema on the insects, stereopsis could be demonstrated.
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In the lilac chaser, we keep our eyes still, so the afterimages grow and are revealed when the stimulus disappears. #When a blurry and non blurry stimulus is presented to a region of the visual field, and we keep our eyes still, that stimulus will disappear even though it is still physically presented. This is called color adaptation. These effects combine to yield the remarkable sight of a green spot running around in a circle on a grey background when only stationary, flashing grey spots have been presented.
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Without treatment, NTG leads to progressive visual field loss and in the last consequence to blindness. The mainstay of conventional glaucoma therapy, reducing IOP by pressure-lowering eye drops or by surgery, is applied in cases of NTG as well. The rationale: the lower the IOP, the less the risk of ganglion cell loss and thus in the long run of visual function. The appearance of disc hemorrhages is always a warning sign that therapeutic approaches are not successful - the small bleedings, usually described as flame-shaped, almost always indicate a progression of the disease.
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Glaucoma is a progressive optic neuropathy where retinal ganglion cells and their axons die causing a corresponding visual field defect. An important risk factor is increased intraocular pressure (pressure within the eye) either through increased production or decreased outflow of aqueous humour. Increased resistance to outflow of aqueous humour may occur due to an abnormal trabecular meshwork or due to obliteration of the meshwork resulting from injury or disease of the iris. However, increased interocular pressure is neither sufficient nor necessary for development of primary open angle glaucoma, although it is a major risk factor.
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CBMM Memo No. 003, Massachusetts Institute of Technology, Cambridge, MA In hierarchical architectures, one layer is not necessarily invariant to all transformations that are handled by the hierarchy as a whole. Some transformations may pass through that layer to upper layers, as in the case of non-group transformations described in the previous section. For other transformations, an element of the layer may produce invariant representations only within small range of transformations. For instance, elements of the lower layers in hierarchy have small visual field and thus can handle only a small range of translation.
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With computer-controlled etching, the technology to create thin plastic sheets with thousands of microscopic ‘prism’ lenses that can magnify or diffract light can be made. Since violet light has more energy than red, and bends more when refracted, some lenses can distort an image if they don’t focus all of the colors at the same point. This distortion is called chromatic aberration. One type of film etching creates lenses that deliberately exaggerate this aberration, separating the colors of an image into different convergence points in the visual field. It’s a patented process called ChromaDepth.
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Symptom-producing, or pathological, scotomata may be due to a wide range of disease processes, affecting any part of the visual system, including the retina (in particular its most sensitive portion, the macula), the optic nerve and even the visual cortex."Bilateral effects of unilateral visual cortex lesions in human", Matthew Rizzo and Donald A. Robin, Brain (1996), 119, pages 951-96. A pathological scotoma may involve any part of the visual field and may be of any shape or size. A scotoma may include and enlarge the normal blind spot.
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According to Vesely, this kind of discrepancy might be useful to understand the nature of the question; and may in fact become a means to understand what impairs the communication between different levels of representation, and conversely, what happens when such communication takes place. Vesely also takes up the example of an experiment that, paradoxically perhaps, was carried out in the hey-day of logical empiricism. The experiment was carried out by Schilder, and involved a temporary inversion of the visual field (pp. 46ss), leaving other perceptual fields untouched.
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When trabectome surgery results are correlated with glaucoma severity, patients with more medication, higher intraocular pressure and worse visual field experience a larger reduction in intraocular pressure than those with less aggressive glaucoma [33,37]. Studies have shown patients with the most advanced glaucoma to have a pressure reduction three times greater than those with mild glaucoma. Individuals with advanced glaucoma have been shown to have a lower success rate than those with mild glaucoma. This risk of failure is important when trabectome surgery is considered as a less risky alternative to traditional procedures.
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Anatomical illustration of human neuroanatomy There is no general consensus on the definition of CBS. Predominant factors correlated with CBS are a decrease of visual acuity, visual field loss, and elderly age. While characteristic features of visual hallucinations are not specifically linked to the anatomical site of the ocular injury, they usually match to the location of visual loss. The most commonly accepted theory for Charles Bonnet Syndrome proposes that extreme visual impairment promotes sensory deafferentation, leading to disinhibition, thus resulting in sudden neural firings of the visual cortical regions.
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The optic nerves from both eyes meet and cross at the optic chiasm, at the base of the hypothalamus of the brain. At this point the information coming from both eyes is combined and then splits according to the visual field. The corresponding halves of the field of view (right and left) are sent to the left and right halves of the brain, respectively, to be processed. That is, the right side of primary visual cortex deals with the left half of the field of view from both eyes, and similarly for the left brain.
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Most causes of lightheadedness are not serious and either cure themselves quickly, or are easily treated. Keeping a sense of balance requires the brain to process a variety of information received from the eyes, the nervous system, and the inner ears. If the brain is unable to process these signals, such as when the messages are contradictory, or if the sensory systems are improperly functioning, an individual may experience lightheadedness or dizziness. Lightheadedness can also be called presyncope, in contrast with syncope (fainting), particularly in cases of temporary visual field loss (i.e.
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Despite their small or absent pinnae, they have a good sense of hearing, although their most important sense appears to be that of touch. Like other rodents, they have an excellent sense of smell, and they are also able to close their nostrils during digging to prevent them from clogging with dirt. The eyes of blesmols are structurally normal, despite their relatively small size, and include normal light-sensitive cells. However, the visual centres of their brains are reduced in certain respects, especially in those centres concerned with localising objects in the visual field.
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New York: McGraw-Hill; 2000. Eran Zaidel also studied such patients and found some evidence for the right hemisphere having at least some syntactic ability. Language is primarily localized in the left hemisphere. One of the experiments carried out by Gazzaniga involved a split-brain male patient sitting in front of a computer screen while having words and images presented on either side of the screen, and the visual stimuli would go to either the right or left visual field, and thus the left or right brain, respectively.
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It was observed that if the patient was presented with an image to his left visual field (right brain), he would report not seeing anything. If he was able to feel around for certain objects, he could accurately pick out the correct object, despite not having the ability to verbalize what he saw. This led to confirmation that the left brain is localized for language whereas the right brain does not have this capability, and when the corpus callosum is cut, the two hemispheres cannot communicate in order for situation-pertinent speech to be produced.
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After visual processing, we consciously perceive this object of focus. In the context of a student in a classroom, the student's eyes focus on a paper on their desk. After his eyes collect light reflected off of the paper and this information is processed in his visual cortex, the student consciously perceives the paper in front of him. #Following either a conscious decision or an involuntary perception of a stimulus in the periphery of the visual field, the eyes intend to move to a second target of interest.
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It was an early smartwatch, powered by a computer on a chip.Japanese PCs (1984) (14:05), Computer Chronicles In 1989, Reflection Technology marketed the Private Eye head-mounted display, which scans a vertical array of LEDs across the visual field using a vibrating mirror. This display gave rise to several hobbyist and research wearables, including Gerald "Chip" Maguire's IBM / Columbia University Student Electronic Notebook,J. Peter Bade, G.Q. Maguire Jr., and David F. Bantz, The IBM/Columbia Student Electronic Notebook Project, IBM, T. J. Watson Research Lab., Yorktown Heights, NY, 29 June 1990.
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Palinopsia necessitates a full ophthalmologic and neurologic history and physical exam. There are no clear guidelines on the work-up for illusory palinopsia, but it is not unreasonable to order automated visual field testing and neuroimaging since migraine aura can sometimes mimic seizures or cortical lesions. However, in a young patient without risk factors or other worrisome symptoms or signs (vasculopathy, history of cancer, etc.), neuroimaging for illusory palinopsia is low-yield but may grant the patient peace of mind. The physical exam and work-up are usually non-contributory in illusory palinopsia.
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It is also possible that impairments in mechanisms that register spatial locations lead to simultanagnosia. According to the feature-integration theory of attention, features of the visual scene, such as color and orientation, are registered early and in parallel across the visual field. These features are represented by separate maps that are later integrated to form a master map of locations that specifies where things are but not what they are. In order to identify objects, focused attention is required to bind perceptual representations of objects being viewed with features in their proper locations.
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Finally, simultanagnosia may result from deficits in spatial indexing. Several studies have noted that a pre-attentive stage of processing exists during which visual features are obtained from the visual field in parallel. Once these features have been extracted, they can be indexed, which allows them to function as anchor points for additional visual routines; visual routines are sequences of elemental operations, such as visual search or texture segregation, which define the spatial relationships among objects as well as their properties. Saliency of a feature facilitates the ease with which it can be indexed.
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Significantly, it produces the highest visual acuity and serves as the center of fixation, only registering a small part of the visual field. Campus's use of zoom mirrors the small section of the world the fovea has access to. Additionally, the circular spotlight silhouetting Campus in the center of the screen references the circular fovea. At this point in the video, the camerawork is no longer tied as directly to the mechanics of human perception as it was before, but uses technological means to reference biological sight, relocating it outside of the body.
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Asomatognosia is the inability to feel, recognize, or be conscious of one's own specific body parts or bodily conditions (Whishaw, 2015). Generally, asomatognosia often arises from damage to the right parietal lobe (Whishaw, 2015). Evidence indicates that damage to the right hemisphere often results from a stroke or pre- existing hemispatial neglect, or inattention to the left visual field (Antoniello, 2016) (Keenan, 2004). Individuals who suffer from somatoparaphrenia, a specific form of asomatognosia, ignore or deny ownership of a body part contralateral to the brain lesion (Feinberg, 1990).
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Superior right quadrantanopia. Quadrantanopia (quadrantanopsia or quadrantic hemianopsia) is decreased vision or blindness in one quarter of the visual field. The particular quarter of vision missing depends on whether the location of the brain damage is temporal or parietal, and the side of the lesion. For example, a lesion to the right temporal lobe with damage specifically to Meyer's loop will give rise to a left upper (superior) quadrantanopsia, while a lesion to the right parietal radiation with damage specifically to Baum's loop will result in a left lower (inferior) quadrantanopsia.
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Circular light targets were used as stimuli. In studies, LM reported some impression of horizontal movement at a speed of 14 degrees of her predetermined visual field per second (deg/s) while fixating in the middle of the motion path, with difficulty seeing motion both below and above this velocity. When allowed to track the moving spot, she had some horizontal movement vision up to 18 deg/s. For vertical movement, the patient could only see motion below 10 deg/s fixated or 13 deg/s when tracking the target.
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If an implant needs to be removed or re-positioned after a few years, complications can occur. The visual cortex is much more complex and difficult to deal with than the other areas where artificial vision are possible, such as the retina or optic nerve. The visual field is much easier to process in different locations other than the visual cortex. In addition, each areas of the cortex is specialized to deal with different aspects of vision, so simple direct stimulation will not provide complete images to patients.
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Injury to the trochlear nerve cause weakness of downward eye movement with consequent vertical diplopia (double vision). The affected eye drifts upward relative to the normal eye, due to the unopposed actions of the remaining extraocular muscles. The patient sees two visual fields (one from each eye), separated vertically. To compensate for this, patients learn to tilt the head forward (tuck the chin in) in order to bring the fields back together—to fuse the two images into a single visual field. This accounts for the “dejected” appearance of patients with “pathetic nerve” palsies.
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Macular degeneration Visual field testing is widely used to monitor pathologies affecting the periphery of vision such as glaucoma. During a conventional test, patients are asked to look steady (fixate) at a visual target, while light stimuli are projected at varying intensities in different retinal locations. This process is not, however, considered accurate in the evaluation of pathologies affecting the central part of the retina (macula and fovea centralis) patients with these pathologies are often unable to fixate reliably. By contrast, fundus perimetry, produces reliable results even in patients with unstable or eccentric fixation.
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The central control of this process, which involves the continuous, precise adjustment of forces on twelve different tendons in order to point both eyes in exactly the same direction, is truly remarkable. The recent discovery of soft tissue pulleys in the orbit – similar to the trochlea, but anatomically more subtle and previously missed – has completely changed (and greatly simplified) our understanding of the actions of the extraocular muscles. Perhaps the most important finding is that a 2-dimensional representation of the visual field is sufficient for most purposes.
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Carcinomas that metastasize into the pituitary gland are uncommon and typically seen in the elderly, with lung and breast cancers being the most prevalent, In breast cancer patients, metastases to the pituitary gland occur in approximately 6-8% of cases.Daniel R. Fassett, M.D.; William T. Couldwell, M.D., PhD;Medscape:Metastases to the Pituitary Gland Symptomatic pituitary metastases account for only 7% of reported cases. In those who are symptomatic Diabetes insipidus often occurs with rates approximately 29-71%. Other commonly reported symptoms include anterior pituitary dysfunction, visual field defects, headache/pain, and ophthalmoplegia.
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Indeed, several works suggest that the most "envious" situation would be to have both many jōrō and many wakashū.Mostow, Joshua S. (2003), "The gender of wakashu and the grammar of desire", in Joshua S. Mostow; Norman Bryson; Maribeth Graybill, Gender and power in the Japanese visual field, University of Hawaii Press, pp. 49–70 Likewise, women were considered to be particularly attracted to both wakashū and onnagata, and it was assumed that many of these young men would reciprocate that interest. Therefore, both many practitioners of nanshoku and the young men they desired would be considered bisexual in modern terminology.
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Pituitary tumors require treatment when they are causing specific symptoms, such as headaches, visual field defects or excessive hormone secretion. Transsphenoidal surgery (removal of the tumor by an operation through the nose and the sphenoidal sinuses) may, apart from addressing symptoms related to the tumor, also improve pituitary function, although the gland is sometimes damaged further as a result of the surgery. When the tumor is removed by craniotomy (opening the skull), recovery is less likely–but sometimes this is the only suitable way to approach the tumor. After surgery, it may take some time for hormone levels to change significantly.
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Optic nerve fibers from the retinas' nasal halves cross to the opposite sides joining the fibers from the temporal halves of the opposite retinas to form the optic tracts. The arrangements of the eyes' optics and the visual pathways mean vision from the left visual field is received by the right half of each retina, is processed by the right visual cortex, and vice versa. The optic tract fibers reach the brain at the lateral geniculate nucleus, and travel through the optic radiation to reach the visual cortex. Hearing and balance are both generated in the inner ear.
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Canthaxanthin and astaxanthin are naturally occurring carotenoids that are used in the British and US food industry to add color to foods such as sausage and fish. Canthaxanthin has been used in over-the-counter “tanning pills” in the United States and Europe, but is not currently Food and Drug Administration (FDA)-approved for this purpose in the United States because of its adverse effects. These include hepatitis, urticaria, aplastic anemia, and a retinopathy characterized by yellow deposits and subsequent visual field defects. Infants and small children are especially prone to carotenoderma because of the cooked, mashed, and pureed vegetables that they eat.
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The new realists did not want to acknowledge representationalism at all but later embraced something akin to Aristotle's form of realism: blackness is a general quality that many objects have in common, and the nervous system selects not just the object but the commonality as a fact. But Arthur Lovejoy showed in his book The Revolt Against Dualism that the perception of black varies so much, depending on context in the visual field, the perceiver's personal history and cultural usage, that it cannot be reduced to commonalities within objects. Better, Lovejoy thought, to bring representational ideas back into the account after all.
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The IMAX flat screen system uses large format film, a wide and deep screen, and close and quite steep "stadium" seating. The effect is to fill the visual field to a greater degree than is possible with conventional wide screen systems. Like the IMAX dome, this is found in major urban areas, but unlike the dome system it is practical to reformat existing movie releases to this method. Also, the geometry of the theater and screen are more amenable to inclusion within a newly constructed but otherwise conventional multiple theater complex than is the dome style theater.
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One wide screen development during the 1950s used non-anamorphic projection, but used three side by side synchronised projectors. Called Cinerama, the images were projected onto an extremely wide, curved screen. Some seams were said to be visible between the images but the almost complete filling of the visual field made up for this. This showed some commercial success as a limited location (only in major cities) exhibition of the technology in This is Cinerama, but the only memorable story-telling film made for this technology was How the West Was Won, widely seen only in its Cinemascope re-release.
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Assorted moths in the University of Texas Insect Collection Moths frequently appear to circle artificial lights, although the reason for this behavior (positive phototaxis) is currently unknown. One hypothesis is called celestial or transverse orientation. By maintaining a constant angular relationship to a bright celestial light, such as the moon, they can fly in a straight line. Celestial objects are so far away that, even after travelling great distances, the change in angle between the moth and the light source is negligible; further, the moon will always be in the upper part of the visual field, or on the horizon.
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Brodmann area 8 The frontal eye fields (FEF) are a region located in the frontal cortex, more specifically in Brodmann area 8 or BA8, of the primate brain. In humans, it can be more accurately said to lie in a region around the intersection of the middle frontal gyrus with the precentral gyrus, consisting of a frontal and parietal portion. The FEF is responsible for saccadic eye movements for the purpose of visual field perception and awareness, as well as for voluntary eye movement. The FEF communicates with extraocular muscles indirectly via the paramedian pontine reticular formation.
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For example, the leaves of a tree or blades of grass give rise to the percept of 'tree-ness' and 'lawn-ness'. It has been demonstrated that individuals have the ability to quickly and accurately encode ensembles of objects, like leaves on a tree, and gather summary statistical information (like the mean and variance) from groups of stimuli. Some research suggests that this process provides rough visual information from the entire visual field, giving way to a complete and accurate picture of the visual world. Although the individual details of this accurate picture might be inaccessible, the 'gist' of the scene remains accessible.
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X-ray image of galaxy cluster Abell 2142 Corona Borealis contains few galaxies observable with amateur telescopes. NGC 6085 and 6086 are a faint spiral and elliptical galaxy respectively close enough to each other to be seen in the same visual field through a telescope. Abell 2142 is a huge (six million light-year diameter), X-ray luminous galaxy cluster that is the result of an ongoing merger between two galaxy clusters. It has a redshift of 0.0909 (meaning it is moving away from us at 27,250 km/s) and a visual magnitude of 16.0. It is about 1.2 billion light-years away.
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Since the initial discovery, a number of more detailed experiments have been performed to further clarify how the left brain "interprets" new information to assimilate and justify it. These experiments have included the projection of specific images, ranging from facial expressions to carefully constructed word combinations, and functional magnetic resonance (fMRI) tests. Many of the studies and experiments build on the initial approach of Gazzaniga in which the right hemisphere is instructed to do things that the left hemisphere is unaware of, e.g. by providing the instructions within the visual field that is only accessible to the right brain.
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Still from a Rana installation monitoring a Bombus terrestris colony Still from a Rana installation monitoring a knapweed flower. A male Bombus lapidarius has been captured pollinating the flower Rana motion vision system is a motion detection that uses vision to detect the presence of objects within its visual field. Rana is based on the open source motion package for Linux, but has significantly enhanced motion detection capabilities. It has been designed top operate as an efficient camera trap system for recording the movements of small invertebrates, capable of operating autonomously in the field for extended periods.
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Variation in color of cats' eyes in flash photographs is largely due to the reflection of the flash by the tapetum. A closeup of a cat's eye Cats have a visual field of view of 200° compared with 180° in humans, but a binocular field (overlap in the images from each eye) narrower than that of humans. As with most predators, their eyes face forward, affording depth perception at the expense of field of view. Field of view is largely dependent upon the placement of the eyes, but may also be related to the eye's construction.
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Due to the number of common features among the multiple syndromes, many suggest that the white dot syndromes are not distinct and represent a spectrum of one disease. Gass described the ‘AZOOR complex’ which consists of MEWDS, MPC, PIC, acute idiopathic blind spot enlargement, acute macular neuroretinopathy, acute annular outer retinopathy, and AZOOR. He suggested these diseases represent one disease due to common factors such as a high occurrence in females, unexplained visual field loss, and reduced electroretinographic amplitudes.Jampol LM, Becker KG. White spot syndromes of the retina: a hypothesis based on the common genetic hypothesis of autoimmune/inflammatory disease.
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Graymatics offers a suite of products that implement its video analysis and image recognition technology. The company’s core product is ContextConnect, an automated, cloud-based technology that identifies and analyzes products within available visual content and provides users with brand and purchasing information. The ContextConnect technology works by identifying and matching relevant visual information with content from its database of scanned images from the Web. Once a product has been identified and tagged within the visual field, the user is provided with a link to an appropriate online retailer from which the product may be purchased.
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Quill B, Henry E, Simon E, O'Brien C: Evaluation of the Effect of Hypercapnia on Vascular Function in Normal Tension Glaucoma. Biomed Res Int 2015, published online October 18 If glaucomatous damage occurs despite normal eye pressure or if glaucomatous damage is progressive despite normalized intraocular pressure, frequently a Flammer syndrome is the cause. In these eyes, an elevated pressure in the retinal veins has been observed. Glaucoma patients with Flammer syndrome show some specific clinical signs like an increased frequency of the following: optic disc haemorrhages, activated retinal astrocytes, elevated retinal venous pressure, optic nerve compartmentalization and fluctuating diffuse visual field defects.
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Each triptych included a selected large-scale photojournalistic image of a crowd; a photographic image of jasmine shrubs taken by the artist, and an engraved bottle containing a jasmine oil composition. The images of crowds were researched for their unique qualities in showing large-visual-field human portraiture and the different socio- dynamics of massing events. In the 2012 exhibition, The Smell of a Critical Moment, a work involving the participation of Occupy Wall Street protestors, she continued her explorations of the multimodal communication systems involved in the underlying chemosensory information exchanged in crowds and then through an immersive installation.
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Prior studies have already shown that blindsight patients are able to detect motion even though they claim they do not see any visual percepts in their blind fields. The subjects of the study were two patients who suffered from hemianopsia—blindness in more than half of their visual field. Both of the subjects had displayed the ability to accurately determine the presence of visual stimuli in their blind hemifields without acknowledging an actual visual percept previously. To test the effect of brightness on the subject's ability to determine motion they used a white background with a series of colored dots.
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His canvases are made of a series of vertical wedges, usually three per work, painted in a realistic style on each side of the wedge. The images are arranged so that, when seen from one point, the images on the various wedges form a realistic whole with slight breaks in the visual field. As the viewer moves in front of the canvas, the images on the various wedges seem to move and swim. Photographs of his canvases give a sense of how they are constructed, but they give no real sense of the illusion of movement.
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Playing some musical wind instruments has been linked to increases in intraocular pressure. A 2011 study focused on brass and woodwind instruments observed "temporary and sometimes dramatic elevations and fluctuations in IOP". Another study found that the magnitude of increase in intraocular pressure correlates with the intraoral resistance associated with the instrument, and linked intermittent elevation of intraocular pressure from playing high-resistance wind instruments to incidence of visual field loss. The range of intraoral pressure involved in various classes of ethnic wind instruments, such as Native American flutes, has been shown to be generally lower than Western classical wind instruments.
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Lateralized stimuli must also be presented very briefly, to eliminate the participant's ability to make an eye-movement toward the lateralized stimulus (which would result in the stimulus no longer being lateralized, and instead projected to both cerebral hemispheres). Since saccadic latencies to a lateralized stimulus can be as fast as 150ms following stimulus onset, the lateralized stimulus should only be presented for a duration of 180ms at most. A free software tool called the "Lateralizer" has been developed for piloting and conducting customizable experiments using the divided visual field paradigm.Motz, B.A., James, K.H., & Busey, T.A. (2012).
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Hemispatial neglect can have a wide range in terms of what the patient neglects. The first range of neglect, commonly referred to as "egocentric" neglect, is found in patients who neglect their own body or personal space. These patients tend to neglect the opposite side of their lesion, based on the midline of the body, head, or retina. For example, in a gap detection test, subjects with egocentric hemispatial neglect on the right side often make errors on the far right side of the page, as they are neglecting the space in their right visual field.
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Classical interference microscopy, also called quantitative interference microscopy, uses two separate light beams with much greater lateral separation than that used in phase contrast microscopy or in differential interference microscopy (DIC). In variants of the interference microscope where object and reference beam pass through the same objective, two images are produced of every object (one being the "ghost image"). The two images are separated either laterally within the visual field or at different focal planes, as determined by the optical principles employed. These two images can be a nuisance when they overlap, since they can severely affect the accuracy of mass thickness measurements.
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Stanford neuroscientist Brian Wandell at Arizona State University SciAPP conference, March 7, 2019. Brian A. Wandell is the Isaac and Madeline Stein Family Professor at Stanford University, where he is Director of the Stanford Center for Cognitive and Neurobiological Imaging, and Deputy Director of the Wu Tsai Neuroscience Institute.Stanford University official biography, accessed March 7, 2019 His work in visual neuroscience uses both functional MRI and computational modeling to understand the action of the visual portions of the brain. His laboratory has worked to develop methods for identifying and measuring visual field maps in visual cortex.
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The initial pointing errors during prism exposure occur in the same direction of the visual shift. For example, if the prismatic goggles displace the visual field to the right, the initial pointing errors would occur to the right of the visual target until a sensory-motor adaptation known as the ‘direct effect of prism adaptation’ occurs. The initial pointing errors induced by the prismatic goggles are caused by the misalignment of the observer's motor and proprioceptive maps. Once the error has been detected, the observer makes a conscious effort to try and fix the error via strategic recalibration.
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At BYBA finals, Trinity came first beating all the other bands in their division. Other awards include, Academy Brass 2006 (Division Two), National Championships (Division Two) in 2006 and 2007, and Ouse Valley Sounds MBC 2008 (Division Two). Following a year away from competing, for the 2014 season, the show band competed in Division 2 of the British Youth Band Association and won the first show of the season, at Music Revolution in Bradford taking Music Effect, Music Analysis, Field Wind, Field Visual, Field Percussion and Colour Guard captions. The Trinity School Show Band ceased to exist in 2017.
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Where this angle is narrowed or closed, pressure increases over time, causing damage to the optic nerve, leading to blindness. Primary open-angle glaucoma (also, primary glaucoma, chronic glaucoma) refers to slow clogging of the drainage canals resulting in increased eye pressure which causes progressive optic nerve damage. This manifests as a gradual loss of the visual field, starting with a loss of peripheral vision, but eventually the entire vision will be lost if not treated. This is the most common type of glaucoma, accounting for 90% of cases in the United States, but fewer in Asian countries.
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The fact that the sensation of Haidinger's brush corresponds with the visual field of the macula means that it can be utilised in training people to look at objects with their macula. People with certain types of strabismus may undergo an adaptation whereupon they look at the object of attention not with their fovea (at the centre of the macula) but with an eccentric region of the retina. This adaptation is known as eccentric fixation. To aid in training a person to look at an object with their fovea rather than their eccentric retinal zone, a training device can be used.
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Ischemic optic neuropathy (ION) is the loss of structure and function of a portion of the optic nerve due to obstruction of blood flow to the nerve (i.e. ischemia). Ischemic forms of optic neuropathy are typically classified as either anterior ischemic optic neuropathy or posterior ischemic optic neuropathy according to the part of the optic nerve that is affected. People affected will often complain of a loss of visual acuity and a visual field, the latter of which is usually in the superior or inferior field. When ION occurs in patients below the age of 50 years old, other causes should be considered.
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The portion of the R cells at the central axis of the ommatidium collectively form a light guide, a transparent tube, called the rhabdom. Although composed of over 16,000 cells, the Drosophila compound eye is a simple repetitive pattern of 700 to 750 of ommatidia, initiated in the larval eye imaginal disc. Each ommatidium consists of 14 neighboring cells: 8 photoreceptor neurons in the core, 4 non-neuronal cone cells and 2 primary pigment cells. A hexagonal lattice of pigment cells insulates the ommatidial core from neighboring ommatidia to optimize coverage of the visual field, which therefore affects the acuity of Drosophila vision.
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The P2 component is generally thought to reflect higher-order perceptual processing and its modulation by attention. However, it has also been linked to prediction of visual word forms. The P2 response to words in highly constraining contexts is often larger than the P2 response to words in less constraining contexts. When experimental participants read words that are presented to the left or right of their visual fixation (stimulating the opposite hemisphere of the brain first), the larger P2 for words in highly constraining contexts is observed only for right visual field presentation (targeting left hemisphere).
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Optical Coherence Tomography can show areas of retinal thickening due to fluid accumulation from macular edema. In the second stage, abnormal new blood vessels (neovascularisation) form at the back of the eye as part of proliferative diabetic retinopathy (PDR); these can burst and bleed (vitreous hemorrhage) and blur the vision, because these new blood vessels are fragile. The first time this bleeding occurs, it may not be very severe. In most cases, it will leave just a few specks of blood, or spots floating in a person's visual field, though the spots often go away after a few hours.
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That is, if the current task is attentionally demanding and its processing exhausts all the available resources, little remains available to process other non-target stimuli in the visual field. Alternatively, if processing requires a small amount of attentional resources, perceptual load is low and attention is inescapably directed to the non-target stimuli. The effects of perceptual load on the occurrence of inattentional blindness is demonstrated in a study by Fougnie and Marois. Here, participants were asked to complete a memory task involving either the simple maintenance of verbal stimuli, or the rearrangement of this material, a more cognitively demanding exercise.
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OPA1 has distinct roles in the fusion of mitochondrial inner membranes during mitochondrial fusion events, and in regulation of cell death. Mitochondria are subcellular structures that generate and transform energy from metabolism into discrete usable units (ATP) for the cell’s functions (See oxidative phosphorylation, electron transport chain). Retinal ganglion cells (neurons), which make up the optic nerve, have a high energy demand and are particularly sensitive to mitochondrial dysfunction. This is especially the case for smaller and less myelinated neurons such as those found in the papillomacular bundle of the retina, which transmit information corresponding to the central visual field.
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With physical improvements such as increased distances between the cornea and retina, increased pupil dimensions, and strengthened cones and rods, an infant's visual ability improves drastically. The neuro- pathway and physical changes that underlie these improvements in vision remains a strong focus in research. Because of an infant's inability to verbally express their visual field, growing research in this field relies heavily on nonverbal cues including an infant's perceived ability to detect patterns and visual changes. The major components of the visual system can be broken up into visual acuity, depth perception, color sensitivity, and light sensitivity.
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Side- view of the human eye, viewed approximately 90° temporal, illustrating how the iris and pupil appear rotated towards the viewer due to the optical properties of the cornea and the aqueous humor. The approximate field of view of an individual human eye (measured from the fixation point, i.e., the point at which one's gaze is directed) varies by facial anatomy, but is typically 30° superior (up, limited by the brow), 45° nasal (limited by the nose), 70° inferior (down), and 100° temporal (towards the temple). For both eyes combined (binocular) visual field is 135° vertical and 200° horizontal.
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The vestibulo-ocular reflex is a reflex eye movement that stabilizes images on the retina during head movement by producing an eye movement in the direction opposite to head movement in response to neural input from the vestibular system of the inner ear, thus maintaining the image in the center of the visual field. For example, when the head moves to the right, the eyes move to the left. This applies for head movements up and down, left and right, and tilt to the right and left, all of which give input to the ocular muscles to maintain visual stability.
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The idea that the flocculus is involved in motor learning gave rise to the “flocculus hypothesis.” This hypothesis argues that the flocculus plays a key role in the vestibulo-ocular system, most importantly the ability for the vestibular system to adapt to a shift in the visual field. The learning of basic motor skills, including walking, balancing, and the ability to sit up, can be attributed to early patterns and pathways associated with the vestibulo-occular reflex and the pathways formed in the cerebellum. Within the cerebellum pathways that contribute to the learning of basic motor skills.
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" Writing for Entertainment Weekly, Owen Gleiberman gave the film an A grade. He wrote, "For once, the visuals in a 3-D movie don't look darkened or distracting. They look sensationally crisp and alive." Richard Corliss of Time who was very critical in 1997 remained in the same mood, "I had pretty much the same reaction: fitfully awed, mostly water-logged." In regards to the 3D effects, he noted the "careful conversion to 3D lends volume and impact to certain moments ... [but] in separating the foreground and background of each scene, the converters have carved the visual field into discrete, not organic, levels.
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A second main function of preattentive processes is to direct focal attention to the most "promising" information in the visual field. There are two ways in which these processes can be used to direct attention: bottom-up activation (which is stimulus-driven) and top-down activation (which is user-driven). In the guided search model by Jeremy Wolfe, information from top-down and bottom-up processing of the stimulus is used to create a ranking of items in order of their attentional priority. In a visual search, attention will be directed to the item with the highest priority.
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Studies have suggested similar mechanisms in the difficulty for older adults, such as age related optical changes that influence peripheral acuity, the ability to move attention over the visual field, the ability to disengage attention, and the ability to ignore distractors. A study by Lorenzo-López et al. (2008) provides neurological evidence for the fact that older adults have slower reaction times during conjunctive searches compared to young adults. Event-related potentials (ERPs) showed longer latencies and lower amplitudes in older subjects than young adults at the P3 component, which is related to activity of the parietal lobes.
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The highest such number that the eye can resolve as stripes, or distinguish from a grey block, is then the measurement of visual acuity of the eye. For a human eye with excellent acuity, the maximum theoretical resolution is 50 CPD (1.2 arcminute per line pair, or a 0.35 mm line pair, at 1 m). A rat can resolve only about 1 to 2 CPD. A horse has higher acuity through most of the visual field of its eyes than a human has, but does not match the high acuity of the human eye's central fovea region.
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Saccadic gaze is the perceptual mechanism through which the eye is inadvertently drawn to external stimulus without the individual's conscious action. An involuntary gaze is most easily drawn by movement or distinct changes in illumination in an individual's visual field. These external stimuli can be beneficial in such situations as the movement of a pedestrian about to walk out onto the road, in turn allowing the driver to take evasive action. Exogenous cues can also be irrelevant, and often dangerous, leading to distraction from goal behaviours, such as the flashing of a cellphone taking one's eyes off the road.
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The outer boundaries of the fovea are visible under a microscope, or with microscopic imaging technology such as OCT or microscopic MRI. When viewed through the pupil, as in an eye exam (using an ophthalmoscope or retinal photography), only the central portion of the fovea may be visible. Anatomists refer to this as the clinical fovea, and say that it corresponds to the anatomical foveola, a structure with a diameter of 0.35 mm corresponding to 1 degree of the visual field. In clinical usage the central part of the fovea is typically referred to simply as the fovea.
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Vision within the fovea is generally called central vision, while vision outside of the fovea, or even outside the foveola, is called peripheral, or indirect vision. A ring-shaped region surrounding the fovea, known as the parafovea, is sometimes taken to represent an intermediate form of vision called paracentral vision. The parafovea has an outer diameter of 2.5 mm representing 8° of the visual field. The macula, the next larger region of the retina, is defined as having at least two layers of ganglia (bundles of nerves and neurons) and is sometimes taken as defining the boundaries of central vs.
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In the context of human vision, the term "field of view" is typically only used in the sense of a restriction to what is visible by external apparatus, like when wearing spectacles or virtual reality goggles. Note that eye movements are allowed in the definition but do not change the field of view. If the analogy of the eye's retina working as a sensor is drawn upon, the corresponding concept in human (and much of animal vision) is the visual field. It is defined as "the number of degrees of visual angle during stable fixation of the eyes".
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Visual cortex: V1; V2; V3; V4; V5 (also called MT) The visual cortex is the largest system in the human brain and is responsible for processing the visual image. It lies at the rear of the brain (highlighted in the image), above the cerebellum. The region that receives information directly from the LGN is called the primary visual cortex, (also called V1 and striate cortex). It creates a bottom-up saliency map of the visual field to guide attention or eye gaze to salient visual locations, hence selection of visual input information by attention starts at V1 along the visual pathway.
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Similarly, two flocks of birds can cross each other in a viewer's visual field, but they will nonetheless continue to be experienced as separate flocks because each bird has a direction common to its flock. This allows people to make out moving objects even when other details (such as the objects color or outline) are obscured. This ability likely arose from the evolutionary need to distinguish a camouflaged predator from its background. The law of common fate is used extensively in user-interface design, for example where the movement of a scrollbar is synchronised with the movement (i.e.
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These narrow field amacrine cells and their overlap in these subunits can allow certain ganglion cells to detect small amounts of movement of a very small spot in a field of vision. One type of narrow field cells that does this is the starburst amacrine cell. Medium field amacrine cells also contribute to vertical communication in the cells of the retina, but much of their overall function is still unknown. Due to the fact that their dendritic arbor size is pretty similar to that of ganglion cells, they could blur the edge of the ganglion cell visual field.
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For instance, the initial overproduction of synapses during development is key to plasticity that occurs in the visual and auditory cortex. In experiments conducted by Hubel and Wiesel, the visual cortex of kittens exhibits synaptic plasticity in the refinement neural connections following visual inputs. Correspondingly, in the absence of such inputs during development, the visual field fails to develop properly and can lead to abnormal structures and behavior. Furthermore, research suggests that this initial overproduction of synapses during developmental periods provides the foundation by which many synaptic connections can be formed, thus resulting in more synaptic plasticity.
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Paris as seen with left homonymous hemianopsia. A homonymous hemianopsia is the loss of half of the visual field on the same side in both eyes. The visual images that we see to the right side travel from both eyes to the left side of the brain, while the visual images we see to the left side in each eye travel to the right side of the brain. Therefore, damage to the right side of the posterior portion of the brain or right optic tract can cause a loss of the left field of view in both eyes.
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New York: Peter Lang on using video games to enhance perceptual and cognitive abilities. A variety of skills were upgraded in video game players, including "improved hand-eye coordination, increased processing in the periphery, enhanced mental rotation skills, greater divided attention abilities, and faster reaction times, to name a few". An important characteristic is the functional increase in the size of the effective visual field (within which viewers can identify objects), which is trained in action games and transfers to new settings. Whether learning of simple discriminations, which are trained in separation, transfers to new stimulus contexts (e.g.
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The horse uses its binocular vision by looking straight at an object, raising its head when it looks at a distant predator or focuses on an obstacle to jump. To use binocular vision on a closer object near the ground, such as a snake or threat to its feet, the horse drops its nose and looks downward with its neck somewhat arched. A horse will raise or lower its head to increase its range of binocular vision. A horse's visual field is lowered when it is asked to go "on the bit" with the head held perpendicular to the ground.
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These include weakness of one side of the body (hemiparesis), loss of vision for one side of the visual field (hemianopia), and cognitive difficulties (affecting learning, memory or language, for example). Epileptic seizures are also a major part of the illness, although these are often partial. Focal motor seizures or epilepsia partialis continua are particularly common, and may be very difficult to control with drugs. In the chronic or residual stage, the inflammation is no longer active, but the sufferer is left with some or all of the symptoms because of the damage that the inflammation has caused.
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Illusory conjunctions are psychological effects in which participants combine features of two objects into one object. There are visual illusory conjunctions, auditory illusory conjunctions, and illusory conjunctions produced by combinations of visual and tactile stimuli. Visual illusory conjunctions are thought to occur due to a lack of visual spatial attention, which depends on fixation and (amongst other things) the amount of time allotted to focus on an object. With a short span of time to interpret an object, blending of different aspects within a region of the visual field – like shapes and colors – can occasionally be skewed, which results in visual illusory conjunctions.
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Breakdown of diagnosis in orbital lymphoproliferative disorders in a Japanese studySymptoms, if any, can be mild even in the presence of significant swelling or masses. Lacrimal gland involvement may cause swelling of the upper eyelid, or proptosis if there is severe swelling. Other orbital masses or inflammation can result in visual disturbance (blurred vision, double vision, visual field impairment), restricted eye movements, pain or discomfort, numbness in the distribution of the supraorbital and/or infraorbital nerves, or proptosis. IgG4-related ophthalmic disease has been estimated to account for approximately 25% of all cases of proptosis, eyelid swelling and other features of orbital swelling.
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A pituitary tumour may compress the optic tracts or the optic chiasm of the optic nerve (II), leading to visual field loss. A pituitary tumour may also extend into the cavernous sinus, compressing the oculuomotor nerve (III), trochlear nerve (IV) and abducens nerve (VI), leading to double-vision and strabismus. These nerves may also be affected by herniation of the temporal lobes of the brain through the falx cerebri. The cause of trigeminal neuralgia, in which one side of the face is exquisitely painful, is thought to be compression of the nerve by an artery as the nerve emerges from the brain stem.
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Conceptually, the laparoscopic approach is intended to minimise post-operative pain and speed up recovery times, while maintaining an enhanced visual field for surgeons. Due to improved patient outcomes, in the last two decades, laparoscopic surgery has been adopted by various surgical sub-specialties, including gastrointestinal surgery (including bariatric procedures for morbid obesity), gynecologic surgery, and urology. Based on numerous prospective randomized controlled trials, the approach has proven to be beneficial in reducing post-operative morbidities such as wound infections and incisional hernias (especially in morbidly obese patients), and is now deemed safe when applied to surgery for cancers such as cancer of colon. Laparoscopic instruments.
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The most common phosphenes are pressure phosphenes, caused by rubbing or applying pressure on or near the closed eyes. They have been known since antiquity, and described by the Greeks. The pressure mechanically stimulates the cells of the retina. Experiences include a darkening of the visual field that moves against the rubbing, a diffuse colored patch that also moves against the rubbing, well defined shapes such as bright circles that exist near or opposite to where pressure is being applied, a scintillating and ever-changing and deforming light grid with occasional dark spots (like a crumpling fly-spotted flyscreen), and a sparse field of intense blue points of light.
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They can describe and explain only a linear size illusion, which is why they do not properly describe or explain the illusions that most people experience. In order to clarify the new paradigm which replaces the old one, it helps to keep in mind that an angle is the difference between two directions from a common point (the vertex). Accordingly, as described below, the visual angle θ is the difference between two real (optical) directions in the field of view, while the perceived visual angle θ′, is the difference by which the directions of two viewed points from oneself appear to differ in the visual field.
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The information sent to the intraparietal sulcus (IPS) of the posterior parietal cortex allows the magnocellular pathway to direct attention and guide saccadic eye movements to follow important moving objects in the visual field. In addition to following objects with the eyes, the IPS sends information to parts of the frontal lobe that allows the hands and arms to adjust their movements to correctly grasp objects based on their size, position, and location. This ability has led some neuroscientists to hypothesize that the purpose of the magnocellular pathway is not to detect spatial locations, but to guide actions related to the position and motion of objects.
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The first test started with a board that had a horizontal row of lights. The subject was told to sit in front of the board and stare at a point in the middle of the lights, then the bulbs would flash across both the right and left visual fields. When the patients were asked to describe afterward what they saw, they said that only the lights on the right side of the board had lit up. Next, when Sperry and Gazzaniga flashed the lights on the right side of the board on the subjects left side of their visual field, they claimed not to have seen any lights at all.
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Put together in modern neuroanatomical terms they mean that a nerve fiber from a fixed retinal location instructs its target neurons in the brain about the presence of a stimulus in the location in the eye's visual field that is imaged there. The orderly array of retinal locations is preserved in the passage from the retina to the brain, and provides what is aptly called a "retinotopic" mapping in the primary visual cortex. Thus in the first instance brain activity retains the relative spatial ordering of the objects and lays the foundations for a neural substrate of visual space. Unfortunately simplicity and transparency ends here.
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For visual course control, flies' optic flow field is analyzed by a set of motion-sensitive neurons. A subset of these neurons is thought to be involved in using the optic flow to estimate the parameters of self-motion, such as yaw, roll, and sideward translation. Other neurons are thought to be involved in analyzing the content of the visual scene itself, such as separating figures from the ground using motion parallax. The H1 neuron is responsible for detecting horizontal motion across the entire visual field of the fly, allowing the fly to generate and guide stabilizing motor corrections midflight with respect to yaw.
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"Producing the image" in Ziegler & Bischof (1993) 5–24 Many birds have an asymmetry in the eye's structure which enables them to keep the horizon and a significant part of the ground in focus simultaneously. The cost of this adaptation is that they have myopia in the lower part of their visual field. Birds with relatively large eyes compared to their body mass, such as common redstarts and European robins sing earlier at dawn than birds of the same size and smaller body mass. However, if birds have the same eye size but different body masses, the larger species sings later than the smaller.
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These retinal ganglion cells form a bundle at the optic disc, which is a part of the optic nerve. The two optic nerves from each eye meet at the optic chiasm, where nerve fibers from each nasal retina cross which results in the right half of each eye's visual field being represented in the left hemisphere and the left half of each eye's visual fields being represented in the right hemisphere. The optic tract then diverges into two visual pathways, the geniculostriate pathway and the tectopulvinar pathway, which send visual information to the visual cortex of the occipital lobe for higher level processing (Whishaw and Kolb, 2015).
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The participant was able to accurately determine the orientation of the line when the target was cued by an arrow before the appearance of the target, even though these visual stimuli did not equal awareness in the subject who had no vision in that area of his/her visual field. The study showed that even without the ability to be visually aware of a stimulus the participant could still focus his/her attention on this object. In 2003, a patient known as TN lost use of his primary visual cortex, area V1. He had two successive strokes, which knocked out the region in both his left and right hemispheres.
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Birds have acute eyesight—raptors (birds of prey) have vision eight times sharper than humans—thanks to higher densities of photoreceptors in the retina (up to 1,000,000 per square mm in Buteos, compared to 200,000 for humans), a high number of neurons in the optic nerves, a second set of eye muscles not found in other animals, and, in some cases, an indented fovea which magnifies the central part of the visual field. Many species, including hummingbirds and albatrosses, have two foveas in each eye. Many birds can detect polarised light. The avian ear is adapted to pick up on slight and rapid changes of pitch found in bird song.
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A recent study tells us that crowding is intense where the distractor and the target are in the same visual field than when they are in separate visual fields despite equal retinal distance. Crowding is also asymmetrical meaning that a single flanker at an eccentric locus higher than the target makes it harder to identify the target than the single flanker at an eccentric locus closer to the fovea. Crowding is not just a spatial phenomenon it happens over time as well, when a target is moving it is found to be more crowded when the flankers are leading than when they follow the target.
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The Groenendael (in English, approximately ) is a variety of dog that is included in the Belgian Shepherd breed, but sometimes treated as a distinct breed. The Groenendael is recognized, either as a breed or a variety of the larger breed, by all major kennel clubs, such as the Kennel Club of the UK. In the American Kennel Club, it is called the Belgian Sheepdog, a term otherwise synonymous with Belgian Shepherd Dog more broadly. This breed is missing an optic chiasm, which surprisingly, shows no visual field deficits. It is identified by a specific eye movement that also occurs in people with a cut optic chiasm.
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Stereo or stereophonic sound is the reproduction of sound using two or more independent audio channels through a symmetrical configuration of loudspeakers in such a way as to create the impression of sound heard from various directions, as in natural hearing. It is often contrasted with monophonic, or "mono" sound, where audio is in the form of one channel, often centered in the sound field (analogous to a visual field). Sound recording and reproduction is an electrical or mechanical inscription and re-creation of sound waves, such as spoken voice, singing, instrumental music, or sound effects. The two main classes of sound recording technology are analog recording and digital recording.
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One such apparatus utilises a rotating polarised plate backlit with a bright white light. Wearing blue spectacles (to enhance the Haidinger's brush image) and an occluder over the other eye, the user will hopefully notice the Haidinger's brush where their macula correlates with their visual field. The goal of the training is for the user to learn to look at the test object in such a way that the Haidinger's brush overlaps the test object (and the viewer is thus now looking at it with their fovea). The reason for such training is that the healthy fovea is far greater in its resolving power than any other part of the retina.
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Assessment of alleged retinal laser injuries. Arch Ophthalmol, 122, 1210–1217 provide one case, an 11-year-old child who temporarily damaged her eyesight by holding an approximately 5 mW red laser pointer close to the eye and staring into the beam for 10 seconds; she experienced scotoma (a blind spot) but fully recovered after three months. Luttrull & Hallisey (1999) describe a similar case, a 34-year-old male who stared into the beam of a class IIIa 5 mW red laser for 30 to 60 seconds, causing temporary central scotoma and visual field loss. His eyesight fully recovered within two days, at the time of his eye exam.
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For their experiment, Van Voorhis and Hillyard (1977) had participants view circular flashes of light to the left and to the right of a central fixation with the right and left flashes occurring independently with each side having flashes 2 to 8 seconds apart (a replication of Eason et al., 1969), the flashes occurring randomly with 1 to 4 seconds between each flash (left or right), or the flashes occurring randomly with 300 to 600ms between each flash. Participants were instructed to either attend to the left visual field, the right visual hemisphere, or both visual hemispheres for a double flash (two flashes within 70ms of each other).
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That movement being perceived will be sent back to the eye, and the brain will perceive what action was completed and will compensate to fit the actual movement desired. This is called corollary discharge, and it is one of the mechanisms in the cerebral cortex to account for spatially accurate vision. Many areas of the brain help with this function, including the frontal eye fields and the lateral intraparietal area, where neurons are active before the saccade is discharged, which brings the new point of focus into the visual field. This presaccadic shift in the neuron’s receptive field excites the neuron before the eye even moves onto the next site.
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In the object recognition unit model by Marr (1980), the process begins with sensory perception (vision) of the object, which results in an initial representation via feature extraction of basic forms and shapes. This is followed by an integration stage, where elements of the visual field combine to form a visual percept image, the 'primary sketch'. This is a dimensional (D) stage with a 'viewer-centered' object representation, where the features and qualities of the object are presented from the viewer's perspective. The next stage is formation of a 3 dimensional (3D) 'object-centered' object representation, where the object's features and qualities are independent of any particular perspective.
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It is the unexpected nature of said stimulus that differentiates inattentional blindness from failures of awareness such as attentional failures like the aforementioned attentional blink. It is critical to acknowledge that occurrences of inattentional blindness are attributed to the failure to consciously attend to an item in the visual field as opposed the absence of cognitive processing. Findings such as inattentional blindness – the failure to notice a fully visible but unexpected object because attention was engaged on another task, event, or object – has changed views on how the brain stores and integrates visual information, and has led to further questioning and investigation of the brain and importantly of cognitive processes.
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The frequency of the phase reversal of the stimulus used can be clearly distinguished in the spectrum of an EEG; this makes detection of SSVEP stimuli relatively easy. SSVEP has proved to be successful within many BCI systems. This is due to several factors, the signal elicited is measurable in as large a population as the transient VEP and blink movement and electrocardiographic artefacts do not affect the frequencies monitored. In addition, the SSVEP signal is exceptionally robust; the topographic organization of the primary visual cortex is such that a broader area obtains afferents from the central or fovial region of the visual field.
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Both the BBC- licensed Dalek Book (1964) and The Doctor Who Technical Manual (1983) describe these items as being part of a sensory array,Harris (1983), p. 22 while in the 2005 series episode "Dalek" they are integral to a Dalek's forcefield mechanism, which evaporates most bullets and resists most types of energy weapons. The forcefield seems to be concentrated around the Dalek's midsection (where the mutant is located), as normally ineffective firepower can be concentrated on the eyestalk to blind a Dalek. Daleks have a very limited visual field, with no peripheral sight at all, and are relatively easy to hide from in fairly exposed places.
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If left untreated, more serious complications could result, including birth defects in pregnancy, increased risk of a miscarriage, bone mineral loss and, in extreme cases, death. Graves' disease is often accompanied by an increase in heart rate, which may lead to further heart complications, including loss of the normal heart rhythm (atrial fibrillation), which may lead to stroke. If the eyes are proptotic (bulging) enough that the lids do not close completely at night, dryness will occur – with the risk of a secondary corneal infection, which could lead to blindness. Pressure on the optic nerve behind the globe can lead to visual field defects and vision loss, as well.
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Likewise, when a spot on the tectum was electrically stimulated, the toad would turn toward a corresponding part of its visual field, providing further evidence of the direct spatial connections. Among Ewert's many experimental goals was the identification of feature detectors, neurons that respond selectively to specific features of a sensory stimulus. Results showed that there were no "worm-detectors" or "enemy-detectors" at the level of the retina. Instead, he found that the optic tectum and the thalamic-pretectal region (in the diencephalon) play significant roles in the analysis and interpretation of visual stimuli (summarized in Ewert 1974, 2004; Ewert and Schwippert 2006).
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An ant trail Foraging ants travel distances of up to from their nest and scent trails allow them to find their way back even in the dark. In hot and arid regions, day-foraging ants face death by desiccation, so the ability to find the shortest route back to the nest reduces that risk. Diurnal desert ants of the genus Cataglyphis such as the Sahara desert ant navigate by keeping track of direction as well as distance travelled. Distances travelled are measured using an internal pedometer that keeps count of the steps taken and also by evaluating the movement of objects in their visual field (optical flow).
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There can also be preserved function in the superior parietal lobe, even with inferior parietal damage. Parietal regions include some neurons with ipsilateral receptive fields, so that while the representation within one hemisphere emphasizes contralateral space overall, some ipsilateral representation is present also. More specifically, the number of left- hemisphere neurons with visual receptive fields at a particular location decreases monotonically as one considers increasingly peripheral locations in the left visual field, and vice versa in the right hemisphere. This might go some way towards explaining why extinction is more severe after right- hemisphere lesions in people, leaving the patient with just the steep gradient of the intact left hemisphere.
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Instead, the bilateral lesions of the flocculus result in saccadic pursuit, in which smooth tracking is replaced by simultaneous rapid movements, or jerking motions, of the eye to follow an object toward the ipsilateral visual field. These lesions also impair the ability to hold the eyes in the eccentric position, resulting in gaze-evoked nystagmus toward the affected side of the cerebellum. Nystagmus is the constant involuntary movements of the eyes; a patient can have either horizontal nystagmus (side-to-side eye movements), vertical nystagmus (up and down eye movements), or rotary nystagmus (circular eye movements). The flocculus also plays a role in keeping the body oriented in space.
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However, the koniocellular layers, intercalated between LGN layers 1–6 send their axons primarily to the cytochrome-oxidase rich blobs of layers 2 and 3 in V1. Axons from layer 6 of visual cortex send information back to the LGN. Studies involving blindsight have suggested that projections from the LGN travel not only to the primary visual cortex but also to higher cortical areas V2 and V3. Patients with blindsight are phenomenally blind in certain areas of the visual field corresponding to a contralateral lesion in the primary visual cortex; however, these patients are able to perform certain motor tasks accurately in their blind field, such as grasping.
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Since the nerve fiber layer has similar stimulation threshold to that of the retinal ganglion cells, axons passing under the epiretinal electrodes are stimulated, creating arcuate percepts, and thereby distorting the retinotopic map. So far, none of the epiretinal implants had light-sensitive pixels, and hence they rely on external camera for capturing the visual information. Therefore, unlike natural vision, eye movements do not shift the transmitted image on the retina, which creates a perception of the moving object when person with such an implant changes the direction of gaze. Therefore, patients with such implants are asked to not move their eyes, but rather scan the visual field with their head.
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277: "Apart from the actual presence of the sensation, perception is markedly deficient or totally absent, the idiot sees but does not look, hears but does not listen, and feels touch and pain but does not refer them in space and time".Evan Marshall, Eye Language: Understanding the Eloquent Eye (1983), p. 82: "In simple terms, the schizophrenic sees but does not look — contrary to the popular belief that schizophrenics do not see their surroundings". Both arrangements suggest that the person is directing their vision towards the thing, but failing to give sufficient attention to notice specific characteristics or implications of what is in the visual field.
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It is produced by certain retinal cells. It is of rather similar composition to the cornea, but contains very few cells (mostly phagocytes which remove unwanted cellular debris in the visual field, as well as the hyalocytes of Balazs of the surface of the vitreous, which reprocess the hyaluronic acid), no blood vessels, and 98–99% of its volume is water (as opposed to 75% in the cornea) with salts, sugars, vitrosin (a type of collagen), a network of collagen type II fibres with the mucopolysaccharide hyaluronic acid, and also a wide array of proteins in micro amounts. Amazingly, with so little solid matter, it tautly holds the eye.
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The ideal visual field is the area in which stimuli are most accurately, rapidly, and efficiently processed by the eye. In humans, this field is thought to be within 20 degrees above or below the vertical meridian of an individual's gaze and 60 degrees either side of the horizontal meridian. If an object is beyond these boundaries it will require eye movement to bring the stimuli out of periphery. By including feedback instruments in the primary field of vision, HUDs allow for the horizon and all associated stimuli to stay in the primary field vision where the information may still be processed and acknowledged by a motorist.
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Patients may have no specific symptoms. In some cases, patients may complain of lessened visual acuity or changes in their perceived visual field, and such changes may be secondary to or different from symptoms normally associated with cataracts or glaucoma. PEX is characterized by tiny microscopic white or grey granular flakes which are clumps of proteins within the eye which look somewhat like dandruff when seen through a microscope and which are released by cells. The abnormal flakes, sometimes compared to amyloid-like material, are visible during an examination of the lens of an eye by an ophthalmologist or optometrist, which is the usual diagnosis.
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A novel approach, recently cleared by the US FDA, is sampling cortisol in saliva over 24 hours, which may be equally sensitive, as late-night levels of salivary cortisol are high in cushingoid patients. Other pituitary hormone levels may need to be ascertained. Performing a physical examination to determine any visual field defect may be necessary if a pituitary lesion is suspected, which may compress the optic chiasm, causing typical bitemporal hemianopia. When any of these tests is positive, CT scanning of the adrenal gland and MRI of the pituitary gland are performed to detect the presence of any adrenal or pituitary adenomas or incidentalomas (the incidental discovery of harmless lesions).
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However, the woman described by Sacks, Susan Barry, a neurobiology professor at Mt. Holyoke College, subsequently published a book, "Fixing My Gaze." The book discusses multiple case histories and details the therapy procedures and the science underlying them. A systematic review of the literature on the effects of vision therapy on visual field defects published in 2007 concluded that it was unclear to what extent patients benefited from vision restoration therapy (VRT) as "no study has given a satisfactory answer." The authors concluded that scanning compensatory therapy (SCT) seemed to provide a more successful rehabilitation, and simpler training techniques, therefore they recommended SCT until the effects of VRT could be defined.
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A graduate of both the Roeper School for Gifted and Talented Children and the New York School of Visual Arts, Rachael's passion for strong visual art has been ever-present throughout her life. From her early film school projects to her recent outings as an exhibited sculptor and multimedia artist, she seeks to explore the visual field as widely and as boldly as the world of audio. She describes her passion for art as "a release from the pressure" of her extensive yet often stressful music career. Upon her return to Vienna, Rachael sought to bring her artistic skills back to the forefront in 2012.
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Illusory palinopsia may occur during a migraine aura, as do other diffuse illusory symptoms such as halos around objects, visual snow, dysmetropsia, and oscillopsia. In a rare migraine subtype known as persistent visual aura without infarction, illusory palinopsia symptoms (prolonged indistinct afterimages, light streaking, and visual trailing) persist after the migraine has abated. Alternatively, up to 10% of all migraineurs report of formed afterimages that only last a couple seconds and do not occur with other illusory symptoms. These momentary afterimages appear at a different location in the visual field than the original stimulus, occur a few times per month, and are affected by external light and motion.
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Superior colliculus The superior colliculus (SC) or optic tectum (OT) is part of the tectum, located in the midbrain, superior to the brainstem and inferior to the thalamus. It contains seven layers of alternating white and grey matter, of which the superficial contain topographic maps of the visual field; and deeper layers contain overlapping spatial maps of the visual, auditory and somatosensory modalities. The structure receives afferents directly from the retina, as well as from various regions of the cortex (primarily the occipital lobe), the spinal cord and the inferior colliculus. It sends efferents to the spinal cord, cerebellum, thalamus and occipital lobe via the lateral geniculate nucleus (LGN).
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Within approximately six months following the infarct, visual acuity improves by three or more lines of vision on the Snellen Chart (the chart with smaller letters on each lower line) in 42.7% of patients, while in 12.4% of patients, vision worsens by three lines. Opposite eye involvement occurs in approximately 15% to 20% of patients with NAION within 5 years.IONDT(The Ischemic Optic Neuropathy Decompression Trial) Study It is not always devastating as visual acuity may remain only moderately impaired. Furthermore, most cases of NAION involve the loss of a hemifield (either the upper or lower half of the visual field, but not both).
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Cone photoreceptor cells in the retina are responsible for color vision, and are categorized as L, M, and S which refer to the wavelengths of light each is sensitive to. L (long) is most sensitive to red, M (medium) to green, and S (short) to blue. L-cones and M-cones are most responsible for visual acuity as they are concentrated in the fovea centralis, the central visual field. Blue cone monochromacy is a severe condition in which the cones sensitive to red or green light are missing or defective, and only S-cones sensitive to blue light and rods which are responsible for night (scotopic) vision are functional.
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Visual neglect (also called hemispatial neglect or unilateral spatial neglect) differs from hemianopsia in that it is an attentional deficit rather than a visual one. Unlike patients with hemianopsia who actually don't see, those with visual neglect have no trouble seeing but are impaired in attending to and processing the visual information they receive. Whereas hemianopsia can be assuaged by allowing patients to move their eyes around a visual scene (ensuring that the entire scene makes it into their intact visual field), neglect cannot. Neglect can also apply to auditory or tactile stimuli and can even leave a patient unaware of one side of his or her own body.
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Throughout his career, he worked closely with friend and mentor Willem Johan Kolff, with whom he was nominated for the Nobel Prize in Physiology or Medicine in 2003. In 1983, he bought Avery Laboratories (now Avery Biomedical Devices), where he worked on neurostimulation and the artificial eye. Dobelle led one of several teams of scientists around the world seeking to develop technology for artificial vision.A bionic visionary for the blind February 19, 2003 Sydney Morning Herald Dobelle's teams developed a brain implant which films the visual field in front of the patient and transmits it to the brain's visual cortex, allowing the patient to see outlines.
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In his classic work The Perception of the Visual World (1950) he rejected the then fashionable theory of behaviorism for a view based on his own experimental work, which pioneered the idea that animals 'sampled' information from the 'ambient' outside world. He studied the concept of optical flow (later published as part of his theory of affordance). According to Gibson, one determines the optical flow (which can be described as the apparent flow of the movement of objects in the visual field relative to the observer) using the pattern of light on the retina. The term 'affordance' refers to the opportunities for action provided by a particular object or environment.
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Playing some wind instruments, in particular those involving high breath pressure resistance, produce increases in intraocular pressure, which has been linked to glaucoma as a potential health risk. One 2011 study focused on brass and woodwind instruments observed "temporary and sometimes dramatic elevations and fluctuations in IOP". Another study found that the magnitude of increase in intraocular pressure correlates with the intraoral resistance associated with the instrument and linked intermittent elevation of intraocular pressure from playing high-resistance wind instruments to incidence of visual field loss. The range of intraoral pressure involved in various classes of ethnic wind instruments, such as Native American flutes, has been shown to be generally lower than Western classical wind instruments.
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For patients with glaucoma and optic nerve atrophy, existing retinal prostheses are not an option since the optic nerve is damaged, therefore a prosthesis using cortical stimulation is a remaining hope to offer some vision function. A cortical visual prosthesis is a promising subject of research because it targets neurons past the site of disease in most blind patients. However, significant challenges remain such as reproducibility in different patients, long-term effects of electrical stimulation, and the higher complexity of visual organization in the primary visual cortex versus that in the retina. Another site of research for a vision prosthesis using cortical stimulation is the optic nerve itself, which contains the nerve fibers responsible for the complete visual field.
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The eye of a bird most closely resembles that of the reptiles. Unlike the mammalian eye, it is not spherical, and the flatter shape enables more of its visual field to be in focus. A circle of bony plates, the sclerotic ring, surrounds the eye and holds it rigid, but an improvement over the reptilian eye, also found in mammals, is that the lens is pushed further forward, increasing the size of the image on the retina.Sinclair (1985) 88–100 Visual fields for a pigeon and an owl Eyes of most birds are large, not very round and capable of only limited movement in the orbits, typically 10-20° (but in some passerines, >80°) horizontally.
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Due to the positioning of this lobe at the back of the head it is not susceptible to much injury but any significant damage to the brain can cause a variety of damage to our visual perception system. Common problems in the occipital lobe are field defects and scotomas, movement and colour discrimination, hallucinations, illusions, inability to recognize words and inability to recognize movement. A study was done in which patients suffered from a tumour on the occipital lobe and the results shows that the most frequent consequence was contralateral damage to the visual field. When damage occurs in the occipital lobe it is most common to see the effects on the opposite side of the brain.
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The main eyes focus accurately on an object at distances from approximately 2 centimetres to infinity, and in practice can see up to about 75 centimetres. Like all jumping spiders, P. labiata can take in only a small visual field at one time, as the most acute part of a main eye can see all of a circle up to 12 millimetres wide at 20 centimetres away, or up to 18 millimetres wide at 30 centimetres away. Jumping spider's main eyes can see from red to ultraviolet. Generally the jumping spider subfamily Spartaeinae, which includes the genus Portia, cannot discriminate objects at such long distances as the members of subfamilies Salticinae or Lyssomaninae can.
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For still scenes, for instance in microscopy, the resolution of a Bayer mask device can be enhanced by microscanning technology. During the process of color co-site sampling, several frames of the scene are produced. Between acquisitions, the sensor is moved in pixel dimensions, so that each point in the visual field is acquired consecutively by elements of the mask that are sensitive to the red, green and blue components of its color. Eventually every pixel in the image has been scanned at least once in each color and the resolution of the three channels become equivalent (the resolutions of red and blue channels are quadrupled while the green channel is doubled).
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Object-based attention refers to the relationship between an ‘object’ representation and a person’s visually stimulated, selective attention, as opposed to a relationship involving either a spatial or a feature representation; although these types of selective attention are not necessarily mutually exclusive. Research into object-based attention suggests that attention improves the quality of the sensory representation of a selected object, and results in the enhanced processing of that object’s features. The concept of an ‘object’, apropos object-based attention, entails more than a physical thing that can be seen and touched. It includes a perceptual unit or group, namely, elements in a visual field (stimuli) organised coherently by Gestalt factors such as collinearity, closure, and symmetry.
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Often this results in distortions of vision that are clearly visible as bowing and blurring when looking at lines on chart paper (or an Amsler grid) within the macular area, or central 1.0 degree of visual arc. Usually it occurs in one eye first, and may cause binocular diplopia or double vision if the image from one eye is too different from the image of the other eye. The distortions can make objects look different in size (usually larger = macropsia), especially in the central portion of the visual field, creating a localized or field dependent aniseikonia that cannot be fully corrected optically with glasses. Partial correction often improves the binocular vision considerably though.
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The main eyes focus accurately on an object at distances from approximately 2 centimetres to infinity, and in practice can see up to about 75 centimetres. Like all jumping spiders, Portias can take in only a small visual field at one time, as the most acute part of a main eye can see all of a circle up to 12 millimetres wide at 20 centimetres away, or up to 18 millimetres wide at 30 centimetres away. Jumping spider's main eyes can see from red to ultraviolet. Generally the jumping spider subfamily Spartaeinae, which includes the genus Portia, cannot discriminate objects at such long distances as the members of subfamilies Salticinae or Lyssomaninae can.
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Overall, 14.5% of patients taking ivabradine experience luminous phenomena (by patients described as sensations of enhanced brightness in a fully maintained visual field). This is probably due to blockage of Ih ion channels in the retina, which are very similar to cardiac If. These symptoms are mild, transient, and fully reversible. In clinical studies, about 1% of all patients had to discontinue the drug because of these sensations, which occurred on average 40 days after the drug was started. In a large clinical trial, bradycardia (unusually slow heart rate) occurred in 2% and 5% of patients taking ivabradine at doses of 7.5 and 10 mg respectively (compared to 4.3% in those taking atenolol).
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To be more specific, in the RFT, examinees are required to sit in a completely dark room without reflecting surfaces where a 3.5 foot luminous square frame with one inch wide sides contains a rod much like one of the sides. The test is properly given after brief (120-second) dark adaptation and the large glowing RFT is seven feet from the subject so it is a dramatic visual display filling much of the visual field. If the test is given with insufficient dark adaptation, many subjects will see the luminous stimulus disappear or fragment when they fixate it visually and a large proportion of them will not happen to report that. The test's validity then is not known.
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Blindsight is the ability of people who are cortically blind due to lesions in their striate cortex, also known as the primary visual cortex or V1, to respond to visual stimuli that they do not consciously see. The majority of studies on blindsight are conducted on patients who have the conscious blindness on only one side of their visual field. Following the destruction of the striate cortex, patients are asked to detect, localize, and discriminate amongst visual stimuli that are presented to their blind side, often in a forced-response or guessing situation, even though they do not consciously recognize the visual stimulus. Research shows that blind patients achieve a higher accuracy than would be expected from chance alone.
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To determine which people qualify for special assistance because of their visual disabilities, various governments have specific definitions for legal blindness. In North America and most of Europe, legal blindness is defined as visual acuity (vision) of 20/200 (6/60) or less in the better eye with best correction possible. This means that a legally blind individual would have to stand from an object to see it—with corrective lenses—with the same degree of clarity as a normally sighted person could from . In many areas, people with average acuity who nonetheless have a visual field of less than 20 degrees (the norm being 180 degrees) are also classified as being legally blind.
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See section "Discussion" in: For pure horizontal rectus muscle surgeries, it is known that vertical deviations, A and V patterns and cyclotropia can be anticipated or avoided by taking certain surgical precautions. Functional considerations: A frequent outcome of strabismus surgery is consecutive microtropia (also known as monofixation syndrome). Functional improvements and further benefits: For a long time it was thought that adult patients with long-standing strabismus could achieve only cosmetic improvement; in recent years there have been cases in which sensory fusion has occurred also in this type of patients provided that postoperative motor alignment is very high. In case of pre-operative inward squint the correction expands the binocular visual field of the patient, improving peripheral vision.
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The visual routines proposed by Ullman are high-level primitives which parse the structure of a scene, extracting spatial information from the base representations. These visual routines are composed of a sequence of elementary visual operators specific to the task at hand. Visual routines differ from the fixed operations of the base representations in that they are not applied uniformly over the entire visual field --- rather, they are only applied to objects or areas specified by the routines. Ullman lists the following as examples of visual operators: shifting the processing focus, indexing a salient item for further processing, spreading activation over an area delimited by boundaries, tracing boundaries, and marking a location or object for future reference.
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This alters the relative importance of different wavelengths in a spectral power distribution to each observer's color perception. As a result, two spectrally dissimilar lights or surfaces may produce a color match for one observer but fail to match when viewed by a second observer. Field-size metameric failure or field-size metamerism occurs because the relative proportions of the three cone types in the retina vary from the center of the visual field to the periphery, so that colors that match when viewed as very small, centrally fixated areas may appear different when presented as large color areas. In many industrial applications, large-field color matches are used to define color tolerances.
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They may have any level of visual impairment from no light perception in either eye through to a visual acuity of 6/60 and/or a visual field of less than 20 degrees. ; H (1-5) – handcycle This class is for athletes who are lower limb amputees, have paraplegia or tetraplegia and ride a handcycle using arms to turn pedals for propulsion. H1–4 cyclists compete in a lying position, whereas H5 cyclists compete in a kneeling position. ; T (1-2) – tricycle This class is for athletes who have a neurological condition or an impairment which has a comparable effect on their cycling so that they are not able to compete on a standard bicycle for reasons of balance.
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H1 exhibits very specific and predictable responses to directional stimuli, characteristics that are greatly beneficial for exploring the neural code because they allow for confident correlations between neural activity and stimuli. H1 neurons are known as Horizontally Sensitive (HS) cell, meaning HS cells depolarize most strongly in response to horizontal stimuli, and hyperpolarize when the direction of motion is opposite. HS cells, and their counterpart Vertically Sensitive (VS) cells, respond to a fixed direction regardless of the color or contrast of the background or the stimulus, making these neuronal systems ideal for testing. H1 exhibits a response to the stimulation of a single ommatidium, and can discriminate between translational motion of 2-3˚ in the visual field.
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Illusory palinopsia is due to an abnormality in the original perception of a stimulus and is similar to a visual illusion: the distorted perception of a real external stimulus. Hallucinatory palinopsia is due to an abnormality after a stimulus has been encoded in visual memory and is similar to a complex visual hallucination: the creation of a formed visual image where none exists. External conditions such as stimulus intensity, background contrast, fixation, and movement typically affect the generation and severity of illusory palinopsia but not hallucinatory palinopsia. Illusory palinopsia consists of afterimages that are short-lived or unformed, occur in the same location in the visual field as the original stimulus, and are continuous or predictable.
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The vestibulo-ocular reflex (VOR) is a reflex eye movement that stabilizes images on the retina during head movement by producing an eye movement in the direction opposite to head movement, thus preserving the image on the center of the visual field. For example, when the head moves to the right, the eyes move to the left, and vice versa. Since slight head movements are present all the time, the VOR is very important for stabilizing vision: patients whose VOR is impaired find it difficult to read, because they cannot stabilize the eyes during small head tremors. The VOR reflex does not depend on visual input and works even in total darkness or when the eyes are closed.
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Occupational therapy for older adults with low vision includes task analysis, environmental evaluation, and modification of tasks or the environment as needed. Many occupational therapy practitioners work closely with optometrists and ophthalmologists to address visual deficits in acuity, visual field, and eye movement in people with traumatic brain injury, including providing education on compensatory strategies to complete daily tasks safely and efficiently. Adults with a stable visual impairment may benefit from occupational therapy for the provision of a driving assessment and an evaluation of the potential to return to driving. Lastly, occupational therapy practitioners enable children with visual impairments to complete self care tasks and participate in classroom activities using compensatory strategies.
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Plasticity of the spinal neural circuitry after injury. Annual Review of Neuroscience. 27:145–167. When a painting is viewed, the brain interprets the total visual field, as opposed to processing each individual pixel of information independently, and then derives an image. At any instant the spinal cord receives an ensemble of information from all receptors throughout the body that signals a proprioceptive “image” that represents time and space, and it computes which neurons to excite next based on the most recently perceived “images.” The importance of the CPG is not simply its ability to generate repetitive cycles, but also to receive, interpret, and predict the appropriate sequences of actions during any part of the step cycle, i.e.
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The cat claustrum has 3 defined zones: (1) the anterior dorsal zone, which connects to the motor and somatosensory cortex, (2) the posterior dorsal zone that has connections to the visual cortex and (3) a third zone that is ventral to visual one and connects to the auditory areas. Sensory input is segregated based on modalities and there is a high preference for peripheral sensory information. In the cat, input is received from various visual cortical areas and projects back to the area. These loops are retinotopical, meaning that regions getting visual input are responsible for the same region in the visual field as the area of the cortex that projects to the claustrum.
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When ripe females are receptive, males will court them, after a chase sequence through aquatic foliage in which several males may pursue an individual female, breaking off to pursue a different female as the opportunity arises, resulting in the aquarium in mad dashes hither and thither. Eventually, close observation will see a male court a female in some secluded area of aquatic foliage. The courting gesture of the male consists of a quivering motion, with a head-down posture, and the 'flicking' of the unpaired fins in such a manner as to generate flashes of yellow colouration in the visual field of the female. These flashes will be readily visible to the observing aquarist.
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At non-towered airports, pilot-controlled lighting may be installed that can be switched on by the pilot via radio. In both cases, the brightness of the lights can be adjusted for day and night operations. Depth perception is inoperative at the distances usually involved in flying aircraft, and so the position and distance of a runway with respect to an aircraft must be judged by a pilot using only two-dimensional cues such as perspective, as well as angular size and movement within the visual field. Approach lighting systems provide additional cues that bear a known relationship to the runway itself and help pilots to judge distance and alignment for landing.
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Touch receptors occur along the inner edges of the keratinised bill, which are collectively known as the "bill tip organ", allowing for highly dexterous manipulations. Seed-eating parrots have a strong tongue (containing similar touch receptors to those in the bill tip organ), which helps to manipulate seeds or position nuts in the bill so that the mandibles can apply an appropriate cracking force. The head is large, with eyes positioned high and laterally in the skull, so the visual field of parrots is unlike any other birds. Without turning its head, a parrot can see from just below its bill tip, all above its head, and quite far behind its head.
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The Optokinetic reflex (or optokinetic nystagmus) stabilizes the image on the retina through visual feedback. It is induced when the entire visual scene drifts across the retina, eliciting eye rotation in the same direction and at a velocity that minimizes the motion of the image on the retina. When the gaze direction deviates too far from the forward heading, a compensatory saccade is induced to reset the gaze to the centre of the visual field. For example, when looking out of the window at a moving train, the eyes can focus on a moving train for a short moment (by stabilizing it on the retina), until the train moves out of the field of vision.
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Some midget retinal ganglion cells oppose L and M cone activity, which corresponds loosely to red-green opponency, but actually runs along an axis from blue-green to magenta. Small bistratified retinal ganglion cells oppose input from the S cones to input from the L and M cones. This is often thought to correspond to blue-yellow opponency but actually runs along a color axis from yellow-green to violet. Visual information is then sent to the brain from retinal ganglion cells via the optic nerve to the optic chiasma: a point where the two optic nerves meet and information from the temporal (contralateral) visual field crosses to the other side of the brain.
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Visual/spatial extinction, also known as pseudohemianopia, is the inability to perceive two simultaneous stimuli in each visual field. Those who show spatial extinction can detect a single item in both the left and right visual fields but, under certain conditions of bilateral double simultaneous stimulation (DSS), fails to detect the item in one field.Iain D. Gilchrist, Glyn W. Humphreys & M. Jane Riddoch (1996): Grouping and Extinction: Evidence for Low-level Modulation of Visual Selection, Cognitive Neuropsychology, 13:8, 1223–1249 It is thus believed that extinction is caused by sensory neglect, and that extinction reflects an attentional deficit rather than a contralesional deficit in primary perceptual processing.Baylis, Gordon C., Jon Driver, and Robert D. Rafal.
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Damage to the optic nerve typically causes permanent and potentially severe loss of vision, as well as an abnormal pupillary reflex, which is important for the diagnosis of nerve damage. Views of Paris showing vision with loss of both temporal visual fields The type of visual field loss will depend on which portions of the optic nerve were damaged. In general, the location of the damage in relation to the optic chiasm (see diagram above) will affect the areas of vision loss. Damage to the optic nerve that is anterior, or in front of the optic chiasm (toward the face) causes loss of vision in the eye on the same side as the damage.
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Bonnet–Dechaume–Blanc syndrome, also known as Wyburn-Mason syndrome, is a rare congenital disorder characterized by arteriovenous malformations of the brain, retina or facial nevi. The syndrome has a number of possible symptoms and can, more rarely, affect the skin, bones, kidneys, muscles, and gastrointestinal tract. When the syndrome affects the brain, people can experience severe headaches, seizures, acute stroke, meningism, and progressive neurological deficits due to acute or chronic ischaemia caused by arteriovenous shunting. In the retina, the syndrome causes retinocephalic vascular malformations that tend to be present with intracranial hemorrhage and lead to decreased visual acuity, proptosis, pupillary defects, optic atrophy, congestion of bulbar conjunctiva, and visual field defects.
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Ptolemy, in his treatise Optics, held an extramission-intromission theory of vision: the rays (or flux) from the eye formed a cone, the vertex being within the eye, and the base defining the visual field. The rays were sensitive, and conveyed information back to the observer's intellect about the distance and orientation of surfaces. He summarized much of Euclid and went on to describe a way to measure the angle of refraction, though he failed to notice the empirical relationship between it and the angle of incidence. Plutarch (1st–2nd century AD) described multiple reflections on spherical mirrors and discussed the creation of magnified and reduced images, both real and imaginary, including the case of chirality of the images.
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Musculoskeletal problems are prevalent among dental professionals. Problems can begin as early on as dental school, with 79% of dental students reporting neck and/or back pain, at one undergraduate dental school in the UK. The problems arise from the nature of the job: focusing on fine procedures which require a close visual field and sustained posture for long periods of time. Musculoskeletal disorders were found to be more prevalent amongst dental surgeons than surgeons or physicians, and 60% of dentists reported symptoms in more than one site. Repetitive work, the need to maintain steady hands, and spending most of the day with an awkward posture can lead to musculoskeletal pain in various sites.
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Li Zhaoping is known as the creater of the V1 Saliency Hypothesis, V1SH (pronounced 'vish'), that the primary visual cortex (V1) in primates creates a saliency map of the visual field to guide visual attention or gaze shifts exogenously. Proposed in the late-1990s, V1SH was unpopular initially, since it was contrary to the main and popular idea that the frontal and parietal areas of the brain are responsible for the saliency map. As V1SH gathered more experimental support, Zhaoping became more sought after for keynote or invited speeches in international conferences ,and V1SH rises from being unpopular to being controversial. Some report experimental data for the theory, while others report evidence against it. .
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A case study described recently in The Irish Medical Journal discussed the role the posterior commissure plays in the connection between the right occipital cortex and the language centers in the left hemisphere. This study explains how visual information from the left side of the visual field is received by the right visual cortex and then transferred to the word form system in the left hemisphere though the posterior commissure and the splenium. Disruption of the posterior commissure can cause alexia without agraphia. It is evident from this case study of alexia without agraphia that the posterior commissure plays a vital role in transferring information from the right occipital cortex to the language centers of the left hemisphere.
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In particular, in cooperation with scholars from Japan (like Hiroshi Shimizu or Tadeshe Kume) this new term and concept has proven to be useful. Research of Ernst Pöppel has globalized in the last years, having moved now more towards the East compared to earlier orientation towards the West, like cooperation with scientists from the US. He has common projects with Chinese colleagues from Peking University (in particular with Yan Bao and Bin Zhou from the Department of Psychology and with Huisheng Chi and Xihong Wu from the Center of Speech and Hearing Research)Bao Y, Pöppel E, Two spatially separated attention systems in the visual field: evidence from inhibition of return. Cognitive Processing, 2007, 8(1): 37-44.
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The horopter as a special set of points of single vision was first mentioned in the eleventh century by Ibn al-Haytham, known to the west as "Alhazen". He built on the binocular vision work of Ptolemy and discovered that objects lying on a horizontal line passing through the fixation point resulted in single images, while objects a reasonable distance from this line resulted in double images. Thus Alhazen noticed the importance of some points in the visual field but did not work out the exact shape of the horopter and used singleness of vision as a criterion. The term horopter was introduced by Franciscus Aguilonius in the second of his six books in optics in 1613.
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The mental world is an ontological category in metaphysics, populated by nonmaterial mental objects, without physical extension (though possibly with mental extension as in a visual field, or possibly not, as in an olfactory field) contrasted with the physical world of space and time populated with physical objects, or Plato's world of ideals populated, in part, with mathematical objects.Synopsis of Consciousness and Berkeley's Metaphysics. ... "What are the basic constituents of the mental world?", Consciousness and Berkley's Metaphysics, Peter B. Lloyd, 2008Gottlob Frege, Foundations of ArithmeticMetaphysics, Richard Taylor, Foundations of Philosophy seriesProblems of Philosophy, Bertrand RussellHistory of Western Philosophy, Bertrand Russell The mental world may be populated with, or framed with, intentions, sensory fields, and corresponding objects.
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But when subjects wear these goggles for a while, something surprising occurs. They adapt and become able to walk around as easily as before. When you ask them whether they adapted by re-inverting their visual field or whether they simply got used to walking around in an upside- down world, they can’t say. So as in our beer-drinking case, either we simply do not have the special, infallible access to our qualia that would allow us to distinguish the two cases, or, perhaps, the way the world looks to us is actually a function of how we respond to the world—in which case qualia are not “intrinsic” properties of experience.
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The progressive nature of and lack of a definitive cure for retinitis pigmentosa contribute to the inevitably discouraging outlook for patients with this disease. While complete blindness is rare, the person's visual acuity and visual field will continue to decline as initial rod photoreceptor and later cone photoreceptor degradation proceeds. Studies indicate that children carrying the disease genotype benefit from presymptomatic counseling in order to prepare for the physical and social implications associated with progressive vision loss. While the psychological prognosis can be slightly alleviated with active counseling the physical implications and progression of the disease depend largely on the age of initial symptom manifestation and the rate of photoreceptor degradation, rather than access to prospective treatments.
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In a frequently-cited paper published in 1944,Köhler, W. & Wallach, H. (1944) Figural after-effects: An investigation of visual processes. Proceedings of the American Philosophical Society, 88, 269–357. Köhler and Wallach presented a series of experiments on figural after-effects. If, for example, an observer stares for about a minute at a fixation point in the center of a visual field that is white except for a large black rectangle on the left side, and then (with the rectangle removed) looks at the center of an array of four evenly-spaced squares, symmetrically arranged around the fixation point, the two squares on the left side will appear farther apart than the ones on the right.
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When the beam entered both eyes in a lateral orientation, the number of streaks reported increased. The orientation of the streaks corresponded to the orientation of the beam entering the eye. Unlike in the previous case, the streaks seen were more abundant in the periphery than the center of visual field. Lastly, when the beam entered the back of the head, only one person reported seeing the LF. From these results, the researchers concluded that at least for the LF seen in this case, the flashes could not be due to Cherenkov radiation effects in the eye itself (although they did not rule out the possibility that the Cherenkov radiation explanation was applicable to the case of the astronauts).
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In the cat, it is observed that A-type horizontal cells have a density of 225 cells/mm2 near the center of the retina and a density of 120 cells/mm2 in more peripheral retina. Horizontal cells and other retinal interneuron cells are less likely to be near neighbours of the same subtype than would occur by chance, resulting in ‘exclusion zones’ that separate them. Mosaic arrangements provide a mechanism to distribute each cell type evenly across the retina, ensuring that all parts of the visual field have access to a full set of processing elements. MEGF10 and MEGF11 transmembrane proteins have critical roles in the formation of the mosaics by horizontal cells and starburst amacrine cells in mice.
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CEV is unrelated to the visual noise seen when the retina is physically stimulated. The retina can be made to produce light patterns of visual noise simply by one rubbing their eyes somewhat forcefully in a manner that increases intraocular pressure. Additionally, retinal noise can be produced by touching near the rear of the eyeball producing pressure phosphenes (for example, if one closes one's eyes, looks all the way left, and lightly touches the rightmost part of the eye socket, this produces visual noise in the shape of a circle that appears at the left side of the visual field – a practice that is neither painful nor dangerous). None of these are closed-eye hallucinations.
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250px Stereophonic sound or, more commonly, stereo, is a method of sound reproduction that creates an illusion of multi-directional audible perspective. This is usually achieved by using two or more independent audio channels through a configuration of two or more loudspeakers (or stereo headphones) in such a way as to create the impression of sound heard from various directions, as in natural hearing. Thus the term "stereophonic" applies to so-called "quadraphonic" and "surround-sound" systems as well as the more common two-channel, two-speaker systems. It is often contrasted with monophonic, or "mono" sound, where audio is heard as coming from one position, often ahead in the sound field (analogous to a visual field).
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Motion silencing stems from the study of change blindness which in essence is the failure to detect change in the visual field. The phenomenon has been studied extensively, by means of such methods as flicker tasks, forced saccade tasks, mudsplashes, disrupted and undisrupted scene transitions, incremental scene rotation, and videos. Research has demonstrated that people often fail to detect significant changes to images when the observer is not attending to the changing object fully, thus if attention is paid to the region where the change is occurring then change can be detected and the effect is forestalled. Even with attention observers sometimes fail to detect change due to incoherency in mental representations.
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Most of the buildings such as the Fortune Centre and the GSM buildings were old buildings renovated new, which allows the whole urban area to shed its historical atmosphere to become a more modern industrially developed place. Analysing the visibility of Sculpture Square, its surrounding isovist spaces are limited by its neighbouring high rise buildings, hence limiting the Sculpture Square building to be seen from a wider visual field in the city. The space syntax of Sculpture Square could be improved by widening the partitions between the low rise buildings of Sculpture Square and the high rise buildings in order to retain its significance as a historical site to its place in the modern city.
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Other advantages can be reducing the motion blur of a moving object and enhancing depth perception of an object by focusing two cameras on the same object or moving the cameras. Active control of the camera view point also helps in focusing computational resources on the relevant element of the scene. In this selective aspect, active vision can be seen as strictly related to (overt & covert) visual attention in biological organisms, which has been shown to enhance the perception of selected part of the visual field. This selective aspect of human (active) vision can be easily related to the foveal structure of the human eye, where in about 5% of the retina more than the 50% of the colour receptors are located.
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Transverse orientation, keeping a fixed angle on a distant source of light for orientation, is a proprioceptive response displayed by some insects such as moths. By maintaining a constant angular relationship to a bright celestial light, such as the moon, they can fly in a straight line. Celestial objects are so far away that, even after travelling great distances, the change in angle between the moth and the light source is negligible; further, the moon will always be in the upper part of the visual field, or on the horizon. When a moth encounters a much closer artificial light and uses it for navigation, the angle changes noticeably after only a short distance, in addition to being often below the horizon.
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When a large part of the visual field moves, a viewer feels like they have moved and that the world is stationary. For example, when one is in a train at a station, and a nearby train moves, one can have the illusion that one's own train has moved in the opposite direction. Common sorts of vection include circular vection, where an observer is placed at the center of rotation of a large vertically- oriented rotating drum, usually painted with vertical stripes; linear vection, where an observer views a field that either approaches or recedes; and roll vection, where an observer views a patterned disk rotating around their line of sight. During circular vection, the observer feels like they are rotating and the drum is stationary.
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Mosby's Dictionary of Medicine, Nursing & Health Professions defines the LGN as "one of two elevations of the lateral posterior thalamus receiving visual impulses from the retina via the optic nerves and tracts and relaying the impulses to the calcarine (visual) cortex". What is seen in the left and right visual field is taken in by each eye and brought back to the optic disc via the nerve fibres of the retina. From the optic disc, visual information travels through the optic nerve and into the optic chiasm. Visual information then enters the optic tract and travels to four different areas of the brain including the superior colliculus, pretectum of the mid brain, the suprachiasmatic nucleus of the hypothalamus, and the lateral geniculate nucleus (LGN).
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A cookiecutter shark long has been calculated to have shed 15 sets of lower teeth by the time it is long, totaling 435-465 teeth. This represents a significant investment of resources and is probably why the shark swallows its old sets of teeth, so that it can recycle the calcium content. Unlike other sharks, the retina of the cookiecutter shark has ganglion cells concentrated in a concentric area rather than in a horizontal streak across the visual field; this may help to focus on prey in front of the shark. This fat shark has been known to travel in schools, which may increase the effectiveness of its lure (see below), as well as discourage counterattacks by much larger predators.
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The symptoms of vestibulocerebellar syndrome vary among patients but are typically a unique combination of ocular abnormalities including nystagmus, poor or absent smooth pursuit (ability of the eyes to follow a moving object), strabismus (misalignment of the eyes), diplopia (double vision), oscillopsia (the sensation that stationary objects in the visual field are oscillating) and abnormal vestibulo-ocular reflex (reflex eye adjustment to stabilize gaze during head movement). Gaze-paretic nystagmus, one of the most common symptoms among patients results in poor gaze-holding due to neuron integrator dysfunction. Rebound nystagmus is also frequently found in conjunction with gaze-paretic nystagmus and is characteristic of cerebellar malfunction. These abnormal eye movements are often the earliest indicators of the disorder and may appear during childhood.
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Over the past century, the way the eyes move in human activities as diverse as playing sport, viewing works of art, piloting aircraft, exploring visual scenes, recognizing face or facial expressions, reading language, and sight-reading of music, has revealed some of the ocular and psychological mechanisms involved in the visual system. The gaze- contingent techniques aim to overcome limitations inherent to simple eye- movement recording. Indeed, due to an imperfect coupling between overt and covert attention, it is not possible to exactly know which visual information the viewer is processing based on the fixation locations. By controlling precisely the information projected in different parts of the visual field, the gaze-contingent techniques permit to disentangle what is fixated and what is processed.
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Photo showing conjunctival vessels dilated at the corneal edge (ciliary flush, circumcorneal flush) and hazy cornea characteristic of acute angle closure glaucoma Open-angle glaucoma is painless and does not have acute attacks, thus the lack of clear symptoms make screening via regular eye check- ups important. The only signs are gradually progressive visual field loss, and optic nerve changes (increased cup-to-disc ratio on fundoscopic examination). About 10% of people with closed angles present with acute angle closure characterized by sudden ocular pain, seeing halos around lights, red eye, very high intraocular pressure (>30 mmHg), nausea and vomiting, suddenly decreased vision, and a fixed, mid-dilated pupil. It is also associated with an oval pupil in some cases.
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Ewert then rotated a rectangular moving bar around the container in an effort to mimic a worm-like prey object; see video. The toad's rate of turning was used to quantify the toad's orienting behavior. Ewert showed, by using spots, bars, and square stimuli of different sizes, that toads snapped at a moving bar which was moving in a direction parallel to its long axis, whereas the same bar oriented perpendicularly to the direction of movement (anti-worm configuration) was ignored as prey. Another experimental setup allowed worm or anti-worm stimuli to traverse the toad's visual field in different direction in the x-y co- ordinates, demonstrating that the worm vs anti-worm discrimination is invariant under changes in the direction of movement.
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For example, the visual field of a bird does not extend behind its body. Fish, on the other hand, rely on both vision and on hydrodynamic signals relayed through its lateral line. Antarctic krill rely on vision and on hydrodynamic signals relayed through its antennae. Recent studies of starling flocks have shown, however, that each bird modifies its position relative to the six or seven animals directly surrounding it, no matter how close or how far away those animals are.M. Ballerini, N. Cabibbo, R. Candelier, A. Cavagna, E. Cisbani, I. Giardina, V. Lecomte, A. Orlandi, G. Parisi, A. Procaccini, M. Viale, and V. Zdravkovic (2008) ‘Interaction ruling animal collective behavior depends on topological rather than metric distance: Evidence from a field study’ PNAS 105:1232-1237.
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This relationship between distance and intimacy, between imagery and sound, is also present in the opening sequence of The Wind Will Carry Us. From the outset, Kiarostami formulates a dialectical relationship between image and sound. The camera moves from long shots of the Land Rover winding its way through the mountain paths to extreme close-ups of the film's protagonist. Concurrently, Kiarostami aurally represents an expanse that extends far beyond what the viewer can see at any moment, even when the camera remains a considerable distance from the subject matter on-screen. Kiarostami establishes numerous spaces beyond the visual field by fragmenting his soundtrack to include other sounds such as birds singing, dogs barking and electronic devices such as cell phones and radios blaring in the distance.
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The bottom-up influence, which is driven by stimulation of sensory receptors, is seen simply when the LIP neurons elicit a rapid response when that distractor is flashed quickly into the visual field, and the eye moves towards the distractor, instead of following to the target of the memory-guided saccade due to the stimulation of the visual receptors with the distractor. Bottom-up processing primarily consists of the brain processing indicating that there is an object in the receptive field, with no understanding of what that object is. Most background and irrelevant stimuli shows low activity in the LIP. This priority map receives input from both the dorsal and ventral streams of processing, which process moving visual stimuli and recognize objects.
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Bakker returns to the Coin Trick analogy from Neuropath's Author Afterword, using the magician as an extended explanatory metaphor to further elucidate Asymptotic Limits of specific Recursive Systems and the Asymptotic Complex of encapsulation regarding the experience of persistent global sufficiency, from where the paper almost certainly gets the former part of its title. As before, Bakker builds on previous exposition reframing the experience of "the Now," with a portion of the draft directly referencing an older blog post. Likewise, he again uses the example of the visual field to propose a similar temporal explanation for the conscious experience the Now. Blind Brain Theory, Bakker writes, argues seemingly natural occurring anosognosias but maintains that this becomes ultimately problematic for our experience of identity and intentions.
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For example, when an object in the periphery of the visual field moves, and a person looks toward it many stages of signal processing are initiated. The initial sensory response, in the retina of the eye, and the final motor response, in the oculomotor nuclei of the brain stem, are not all that different from those in a simple reflex, but the intermediate stages are completely different. Instead of a one or two step chain of processing, the visual signals pass through perhaps a dozen stages of integration, involving the thalamus, cerebral cortex, basal ganglia, superior colliculus, cerebellum, and several brainstem nuclei. These areas perform signal-processing functions that include feature detection, perceptual analysis, memory recall, decision-making, and motor planning.
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While tonometry, the measuring of IOP and thus a classical instrument in the diagnosis of glaucoma, is not helpful, ophthalmoscopy leads to the diagnosis by showing typical glaucomatous damage, primarily at the optic nerve head, in the absence of elevated IOP. While the excavation of the optic nerve head and the thinning of its rim appear in all kinds of glaucoma (with high tension and with normal tension, in Primary open angle glaucoma (POAG) and in secondary glaucoma), small hemorrhages close to the optic disc have been identified as a characteristic clinical sign of normal tension glaucoma. Visual field is very important to detect NTG. It shows a defect that typically appear deeper, steeper and closer to fixation comparing to patients with POAG.
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Types of communicative pointing may be divided by linguistic function into three main groups: # Objective pointing - pointing to an object within the visual field of both the pointer and the receiver, such as pointing to a chair which is physically present # Syntactic or anaphoric pointing - pointing to linguistic entities or expressions previously identified, such as pointing to the chair which is not physically present # Imaginative pointing - pointing to things that exist in the imagination, such as pointing to a fictional or remembered chair Additionally, pointing in children who are deaf may be divided between diectic or "natural" pointing, which is shared with hearing children, and symbolic pointing used specifically in sign language, learned by observing and imitating others who sign.
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Because of the similarity in the visual performance of each eye in the intermediate range the brain is able to fuse the images between the eyes rendering a binocular visual environment. This is in contradiction to traditional monovision where the image disparity between the eyes is too high for image fusion by the brain and instead the brain needs to apply suppression of the blurred eye in order to perceive a clear visual field. In Laser Blended Vision, the eyes are effectively working together to allow good vision at near, intermediate and far, without the use of glasses. The effects of Laser Blended Vision tend to last between 5 and 10 years but can be further adjusted by enhancement procedures.
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Stratton continued his experiments on perception, branching into studies on pseudoscopic vision, stereoscopic acuity, eye movements, symmetry and visual illusions, how people perceive depth seeing surroundings either one-eyed or two-eyed, acuity and limits of peripheral vision, apparent motion, afterimages impressed on the eye when a person stares at an object for long and then looks away, and problems with sight in half the visual field (hemianopsia). He both reviewed earlier studies on motion and conducted two of his own, concluding perceiving movement was more than the sum of seeing successive sequential images. He also surveyed and reported in reviews in the Psychological Bulletin experiments at various labs, including those in Europe, on matters related to sensation and perception.
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Some have speculated that, having extracted the hypothesized motion signals (first- or second- order) from the retinal image, the visual system must integrate those individual local motion signals at various parts of the visual field into a 2-dimensional or global representation of moving objects and surfaces. (It is not clear how this 2D representation is then converted into the perceived 3D percept) Further processing is required to detect coherent motion or "global motion" present in a scene. The ability of a subject to detect coherent motion is commonly tested using motion coherence discrimination tasks. For these tasks, dynamic random-dot patterns (also called random dot kinematograms) are used that consist in 'signal' dots moving in one direction and 'noise' dots moving in random directions.
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The information sent to the Intraparietal Sulcus (IPS) of the posterior parietal cortex allows the M pathway to direct attention and guide saccadic eye movements to follow important moving objects in the visual field. In addition to following objects with the eyes, the IPS sends information to parts of the frontal lobe that allows the hands and arms to adjust their movements to correctly grasp objects based on their size, position, and location. This ability has led some neuroscientists to hypothesize that the purpose of the M pathway is not to detect spatial locations, but to guide actions related to the position and motion of objects. Some information has also been found to support the hypothesis that the M pathway is necessary for facial processing.
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The original study by Huges and Zimba started off as an extension of the various studies done revolving around the concept of directed attention, its spatial characteristics and the movement of attention to different locations within the visual field. Their first experiment aimed to determine whether visual performance varied for locations across the vertical and horizontal meridian based on expectancy and to check if attention can be directed both vertically and horizontally. The results showed that cues directed to locations on both the vertical meridian and the horizontal meridian, have similar attentional costs and benefits. Nevertheless, they also reported that subjects have larger decrements in performance when their attention crosses the vertical meridian than when it crosses the horizontal meridian (Huges and Zimba, 1987).
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Growth hormone deficiency is more common in people with an underlying tumor than those with other causes. Sometimes, there are additional symptoms that arise from the underlying cause; for instance, if the hypopituitarism is due to a growth hormone-producing tumor, there may be symptoms of acromegaly (enlargement of the hands and feet, coarse facial features), and if the tumor extends to the optic nerve or optic chiasm, there may be visual field defects. Headaches may also accompany pituitary tumors, as well as pituitary apoplexy (infarction or haemorrhage of a pituitary tumor) and lymphocytic hypophysitis (autoimmune inflammation of the pituitary). Apoplexy, in addition to sudden headaches and rapidly worsening visual loss, may also be associated with double vision that results from compression of the nerves in the adjacent cavernous sinus that control the eye muscles.
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Bálint's syndrome symptoms can be quite debilitating since they impact visuospatial skills, visual scanning and attentional mechanisms. Since it represents impairment of both visual and language functions, it is a significant disability that can affect the patient's safety—even in one's own home environment, and can render the person incapable of maintaining employment. In many cases the complete trio of symptoms—inability to perceive the visual field as a whole (simultanagnosia), difficulty in fixating the eyes (oculomotor apraxia), and inability to move the hand to a specific object by using vision (optic ataxia)—may not be noticed until the patient is in rehabilitation. Therapists unfamiliar with Bálint's syndrome may misdiagnose a patient's inability to meet progress expectations in any of these symptom areas as simply indicating incapability of benefiting from further traditional therapy.
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The discovery of the condition known as blindsight raised questions about how different types of visual information, even unconscious information, may be affected and sometimes even unaffected by damage to different areas of the visual cortex. Previous studies had already demonstrated that even without conscious awareness of visual stimuli humans could still determine certain visual features such as presence in the visual field, shape, orientation and movement. But, in a newer study evidence showed that if the damage to the visual cortex occurs in areas above the primary visual cortex the conscious awareness of visual stimuli itself is not damaged. Blindsight is a phenomenon that shows that even when the primary visual cortex is damaged or removed a person can still perform actions guided by unconscious visual information.
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Vision restoration therapy (VRT) is a computer-based treatment which claims to help with visual field defects regain visual functions through repetitive light stimulation.Marshall RS, Ferrera JJ, Barnes A, Zhang X, O'Brien KA, Chmayssani M, Hirsch J, Lazar RM (2007). Brain activity associated with stimulation therapy of the visual border- zone in hemianopic stroke patients. Neurorehabilitation and Neural Repair; 22(2): 136-144 As the device used in VRT is similar to the DynaVision 2000 that already exist the Food and Drug Administration (FDA) allowed an indication for use "...the diagnosis and improvement of visual functions in patients with impaired vision that may result from trauma, stroke, inflammation, surgical removal of brain tumors or brain surgery, and may also be used to improve visual function in patients with amblyopia".
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The main point is that within these PNGs exist neurons, called binding neurons, that learn to represent the hierarchical binding relationships between lower and higher level visual features in the hierarchy of visual primitives, at every spatial scale and across the entire visual field. This observation is consistent with the hierarchical nature of primate vision proposed by the two neuroscientists John Duncan and Glyn W. Humphreys almost thirty years ago. Furthermore this proposed mechanism for solving the binding problem suggests that information about visual features at every spatial scale, including the binding relations between these features, would be projected upwards to the higher layers of the network, where spatial information would be available for readout by later brain systems to guide behavior. This mechanism has been called the holographic principle.
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Dissociated rat cortical neurons were integrated into a closed stimulus-response feedback loop to control an animat in a virtual environment. A closed-loop stimulus-response system has also been constructed using an MEA by Potter, Mandhavan, and DeMarse, and by Mark Hammond, Kevin Warwick, and Ben Whalley in the University of Reading. About 300,000 dissociated rat neurons were plated on an MEA, which was connected to motors and ultrasound sensors on a robot, and was conditioned to avoid obstacles when sensed. Along these lines, Shimon Marom and colleagues in the Technion hooked dissociated neuronal networks growing on MEAs to a Lego Mindstorms robot; the visual field of the robot was classified by the network, and commands were delivered to the robot wheels such that it completely avoids bumping into obstacles.
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In addition Vanier has been able to perfectly recreate the visual field along the scenic tall mountains and vast (also the main protagonists of the film) and you are not limited to telling the original story, but it has enriched, taking cue to give life to his new staff and transposition, where the most interesting aspect, is due to the shots of the landscape that reveal the past of a documentary filmmaker. Félix Bossuet, the boy who plays the main role, was chosen from more than 2,400 children from the same director candidates because of a "lightning strike" as stated by Vanier. Mehdi El Glaoui, the son of Cécile Aubry, who played Sebastian in the TV series of the same name in the 1960s, has a small role in the film as André.
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In 2014, Simon Cooke - an engineer in Microsoft's Xbox Advanced Technology group - proposed that ocular microtremors might be used by the eye in combination with the retinal cone cell's directional response to light, using the edge-triggered behavior of center- on/surround-off / center-off/surround-on retinal glial cells to super-sample the visual field at higher fidelity than either the Rayleigh criterion or the distribution of cones on the retina allows via simple light capture. He proposed that the frequency of the ocular microtremors might also explain why there is a threshold at half that rate (~43Hz) which determines whether films look 'cinematic' (below 43Hz, or 24 frames per second) or not (above 43Hz - for example, 48 frames per second). He also postulated that this increases the enjoyment and immersion of videogames.
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Lazzarini's installation "skulls" was first exhibited in the Whitney Museum of American Art in the 2001 exhibition, "Bitsreams," and brought the artist into wider public visibility. The installation was made up of four sculptural variations based on a specific human skull, each mounted to one wall at eye level in an offset square room measuring fifteen by fifteen feet. Bathed in diffused fluorescent light, the shadows within the room heightened the works “image aspect” where “the walls of the gallery become a kind of uninflected visual field against which the form of each object is defined.” The experience presented a new type of embodied viewing wherein “You feel the space around you begin to ripple, to bubble, to infold, as if it were becoming unstuck from the fixed coordinates of its three-dimensional extension.
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The vertical–horizontal illusion where the vertical line is thought to be longer than the horizontal Ponzo illusion Illusions can be based on an individual's ability to see in three dimensions even though the image hitting the retina is only two dimensional. The Ponzo illusion is an example of an illusion which uses monocular cues of depth perception to fool the eye. But even with two- dimensional images, the brain exaggerates vertical distances when compared with horizontal distances, as in the vertical-horizontal illusion where the two lines are exactly the same length. In the Ponzo illusion the converging parallel lines tell the brain that the image higher in the visual field is farther away, therefore, the brain perceives the image to be larger, although the two images hitting the retina are the same size.
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Additionally, some processing of the visual field that corresponds to the ventral stream of visual processing occurs in the lower portion of the superior temporal gyrus closest to the superior temporal sulcus. The medial and ventral view of the brain – meaning looking at the medial surface from below the brain, facing upwards – reveals that the inferior temporal gyrus is separated from the fusiform gyrus by the occipital-temporal sulcus. This human inferior temporal cortex is much more complex than that of other primates: non-human primates have an inferior temporal cortex that is not divided into unique regions such as humans' inferior temporal gyrus, fusiform gyrus, or middle temporal gyrus. This region of the brain corresponds to the inferior temporal cortex and is responsible for visual object recognition and receives processed visual information.
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A scotoma is an area of lost or depressed vision within the visual field, surrounded by an area of less depressed or of normal vision. Traquair described the scotoma which bears his name as follows:‘At the chiasmal termination of the nerve the crossed and uncrossed fibres separate, and a small lesion may occur at this point and effect the crossed fibres only, producing a unilateral temporal hemianopic or quadrantic central scotoma called ‘‘junction’’ scotoma, since it indicates the site of the lesion at the junction of the optic nerve and chiasma’.Traquair HM in Clinical perimetry, Scott, GI.(ed), London: Henry Kimpton, 1957 The 'Traquair scotoma' or 'Traquair junctional scotoma' is found in 1 – 10% of patients with pituitary adenomaElkington. SG. Pituitary adenoma, preoperative symptomatology in a series of 260 patients.
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To minimise the effect of eye motion while the animal moves, most such eyes have stabilising eye muscles. The ocelli of insects bear a simple lens, but their focal point always lies behind the retina; consequently, they can never form a sharp image. Ocelli (pit-type eyes of arthropods) blur the image across the whole retina, and are consequently excellent at responding to rapid changes in light intensity across the whole visual field; this fast response is further accelerated by the large nerve bundles which rush the information to the brain. Focusing the image would also cause the sun's image to be focused on a few receptors, with the possibility of damage under the intense light; shielding the receptors would block out some light and thus reduce their sensitivity.
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Along with proprioception and vestibular function, the visual system plays an important role in the ability of an individual to control balance and maintain an upright posture. When these three conditions are isolated and balance is tested, it has been found that vision is the most significant contributor to balance, playing a bigger role than either of the two other intrinsic mechanisms. The clarity with which an individual can see his environment, as well as the size of the visual field, the susceptibility of the individual to light and glare, and poor depth perception play important roles in providing a feedback loop to the brain on the body's movement through the environment. Anything that affects any of these variables can have a negative effect on balance and maintaining posture.
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A more recent (2005) review concluded less positively that: "Less robust, but believable, evidence indicates visual training may be useful in developing fine stereoscopic skills and improving visual field remnants after brain damage. As yet there is no clear scientific evidence published in the mainstream literature supporting the use of eye exercises in the remainder of the areas reviewed, and their use therefore remains controversial." In 2006, noted neurologist Oliver Sacks published a case study about "Stereo Sue", a woman who had regained her stereo vision, absent for 48 years, after undergoing vision therapy. The article was published in The New Yorker magazine, which is fact-checked but not peer-reviewed, very few details were given of the exact therapies used and the article discussed only one case of stereopsis recovery.
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When used as a screening test, subjects that reach this level need no further investigation, even though the average visual acuity with a healthy visual system is typically better. Some people may suffer from other visual problems, such as severe visual field defects, color blindness, reduced contrast, mild amblyopia, cerebral visual impairments, inability to track fast-moving objects, or one of many other visual impairments and still have "normal" visual acuity. Thus, "normal" visual acuity by no means implies normal vision. The reason visual acuity is very widely used is that it is easily measured, its reduction (after correction) often indicates some disturbance, and that it often corresponds with the normal daily activities a person can handle, and evaluates their impairment to do them (even though there is heavy debate over that relationship).
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The vertebral artery supplies the part of the brain that lies in the posterior fossa of the skull, and this type of stroke is therefore called a posterior circulation infarct. Problems may include difficulty speaking or swallowing (lateral medullary syndrome); this occurs in less than a fifth of cases and occurs due to dysfunction of the brainstem. Others may experience unsteadiness or lack of coordination due to involvement of the cerebellum, and still others may develop visual loss (on one side of the visual field) due to involvement of the visual cortex in the occipital lobe. In the event of involvement of the sympathetic tracts in the brainstem, a partial Horner's syndrome may develop; this is the combination of a drooping eyelid, constricted pupil, and an apparently sunken eye on one side of the face.
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The first and second prototype, while maintaining the same velatura biplana at positive scaling, differed due to the different solution in the central link of the wing plane higher than fuselage, where the montantini perpendicular to the first one were substituted with those divaricated in the second one to allow a better visual field to the [pilot aviator], while the two wing planes were connected to each other by a one pair per side of interlocking posts. The two prototypes supported a series of tests until April 28, 1917, revealing that the aircraft possessed flight characteristics and lower performance than those already in line, so no subsequent supply order was issued and the project was abandoned. There is no definite information on the use of the third prototype, nor has it ever actually been completed.
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Each retina of the black-chested buzzard-eagle has two foveaeSchematic diagram of retina of right eye, loosely based on Sturkie (1998) 6 The forward-facing eyes of a bird of prey give binocular vision, which is assisted by a double fovea. The raptor's adaptations for optimum visual resolution (an American kestrel can see a 2–mm insect from the top of an 18–m tree) has a disadvantage in that its vision is poor in low light level, and it must roost at night. Raptors may have to pursue mobile prey in the lower part of their visual field, and therefore do not have the lower field myopia adaptation demonstrated by many other birds. Scavenging birds like vultures do not need such sharp vision, so a condor has only a single fovea with about 35,000 receptors mm2.
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For comparison, Trite auricoma swivels towards a movement up to 75 cm away and approaches targets from about 20 cm. Perhaps P. schultzi gains little from being alerted to objectives at distances because this spider moves so slowly that it is very unlikely to reach a more distant target in time to catch it. Like all jumping spiders, P. schultzi can take in only a small visual field at one time, as the most acute part of a main eye can see all of a circle up to 12 millimeters wide at 20 centimeters away, or up to 18 millimeters wide at 30 centimeters away. A Portia spider takes a relatively long time to see objects, possibly because getting a good image out of such tiny eyes is a complex process and needs a lot of scanning.
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" Federation Equestre International defines this classification as "At this level the rider will ride an elementary/medium level test" The Australian Paralympic Committee defined this classification as: "Grade IV: Athletes with a physical disability or vision impairment. Riders have a physical impairment in one or two limbs (for example limb loss or limb deficiency), or some degree of visual impairment (B2)." As of July 2016, the International Paralympic Committee defines Grade 4 on their website as "Athletes in Grade IV have a mild impairment of range of movement or muscle strength or a deficiency of one limb or mild deficiency of two limbs. Grade IV also includes athletes with visual impairment equivalent to B2 with a higher visual acuity than visually impaired athletes competing in the Grade IIIsport class and/ or a visual field of less than 5 degrees radius.
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On the other hand, this clause led to license compatibility problems of the JSON license with other open-source licenses.Apache and the JSON license on LWN.net by Jake Edge (November 30, 2016) A precursor to the JSON libraries was used in a children's digital asset trading game project named Cartoon Orbit at Communities.com (the State co- founders had all worked at this company previously) for Cartoon Network, which used a browser side plug-in with a proprietary messaging format to manipulate DHTML elements (this system is also owned by 3DO). Upon discovery of early Ajax capabilities, digiGroups, Noosh, and others used frames to pass information into the user browsers' visual field without refreshing a Web application's visual context, realizing real-time rich Web applications using only the standard HTTP, HTML and JavaScript capabilities of Netscape 4.0.5+ and IE 5+.
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For example, a stroke affecting the right parietal lobe of the brain can lead to neglect for the left side of the visual field, causing a patient with neglect to behave as if the left side of sensory space is nonexistent (although they can still turn left). In an extreme case, a patient with neglect might fail to eat the food on the left half of their plate, even though they complain of being hungry. If someone with neglect is asked to draw a clock, their drawing might show only the numbers 12 to 6, or all 12 numbers might be on one half of the clock face with the other half distorted or blank. Neglect patients may also ignore the contralesional side of their body; for instance, they might only shave, or apply make-up to, the non-neglected side.
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Of the several causes for glaucoma, ocular hypertension (increased pressure within the eye) is the most important risk factor in most glaucomas, but in some populations, only 50% of people with primary open-angle glaucoma actually have elevated ocular pressure. Ocular hypertension--an intraocular pressure above the traditional threshold of 21 mm Hg or even above 24 mm Hg--is not necessarily a pathological condition but it increases the risk of developing glaucoma. One study found a conversion rate of 18% within 5 years, meaning less than 1 in 5 people with an elevated intraocular pressure will develop glaucomatous visual field loss over that period of time. It is a matter of debate whether every person with an elevated intraocular pressure should receive glaucoma therapy; currently most ophthalmologists favor treatment of people with additional risk factors.
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Through experimentation, they found that each neuron in the cortex is responsible for a small region of the visual field and also has its own orientation specificity. From the results of these single cell readings in the striate cortex and lateral geniculate, Hubel and Wiesel postulated that simple cortical receptive fields gain complexity and an intricate spatial arrangement through the patterned convergence of multiple "on" or "off" projections from lateral geniculate cells onto single cortical cells. Hubel and Wiesel's investigation of the cat visual cortex sparked interest in the feature detection hypothesis and its relevance to other sensory systems. In fact, T.H. Bullock contended in 1961 that the vestibular system was being ignored by most of the contemporary sensory system research, and he suggested that the equivalent stimulation of vestibular organs may yield similarly intriguing results.
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Further elaborating, Bakker cites the phenomenon in psychophysics known as flicker fusion (or flicker fusion threshold), the point at which consciousness perceives a light as steady. This phenomenon is widely exploited in the modern human environment from light bulbs to screened devices and brings about similar explanatory power akin to Bakker's use of the visual field metaphor. Nearing the close of The Last Magic Show, Bakker delves into the highly speculative implications of Blind Brain Theory's argument for the appearance of consciousness regarding the use and reference of Intentionality in academic philosophy, as well as, the very underpinnings of humanity's scientific and philosophic endeavours, logic and math, the latter of which might reference an earlier essayistic work posted to Three Pound Brain. He also writes of the "First-person Perspective Show," which almost definitely precedes his draft paper, The Introspective Peep Show.
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This suggests that if one has had much experience with the stimuli in a visual field, they are more likely to consciously perceive the unexpected object. In 2011, Elizabeth Graham and Deborah Burke conducted a study that assessed whether or not older adults are more susceptible to inattentional blindness than younger adults by having 51 younger-aged participants (17 to 22 years) and 61 older-aged participants (61 to 81 years) watch the classic gorilla video. Overall, they found that younger-aged participants were more likely to notice the unexpected gorilla than older-aged participants. In a 2015 study, Cary Stothart, Walter Boot, and Daniel Simons attempted to replicate and extend the findings from both Graham and Burke's 2011 study and Steven Most and colleague's 2000 study PhilPapers: MOSSIB on Amazon Mechanical Turk using a sample of 515 participants that varied in age.
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By making 80% trials valid and 20% trials invalid, Posner encourages covert shifts of attention to take place in response to cueing. The ratio makes it beneficial for a participant to covertly shift attention towards the cued location, as it would be an accurate predictor for the majority of the time, giving rise to quicker target detection and response. When we attend to a location, even without directly looking at it, it facilitates processing and decreases the time we need to respond to information occurring in that given space. This results in decreased reaction times in Posner's spatial cueing task for validly cued targets, and slower reaction times in response to invalidly cued targets: "Detection latencies are reduced when subjects receive a cue that indicates where in the visual field the signal will occur" (Posner, Snyder & Davidson, 1980).
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Celestial objects are so far away, even after traveling great distances, the change in angle between the moth and the light source is negligible; further, the moon will always be in the upper part of the visual field or on the horizon. When a moth encounters a much closer artificial light and uses it for navigation, the angle changes noticeably after only a short distance, in addition to being often below the horizon. The moth instinctively attempts to correct by turning toward the light, causing airborne moths to come plummeting downwards, and at close range, which results in a spiral flight path that gets closer and closer to the light source. Other explanations have been suggested, such as the idea that moths may be impaired with a visual distortion called a Mach band by Henry Hsiao in 1972.
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In primates, eye movements can be divided into several types: fixation, in which the eyes are directed toward a motionless object, with eye movements only to compensate for movements of the head; smooth pursuit, in which the eyes move steadily to track a moving object; saccades, in which the eyes move very rapidly from one location to another; and vergence, in which the eyes move simultaneously in opposite directions to obtain or maintain single binocular vision. The superior colliculus is involved in all of these, but its role in saccades has been studied most intensively. Each of the two colliculi — one on each side of the brain — contains a two-dimensional map representing half of the visual field. The fovea — the region of maximum sensitivity — is represented at the front edge of the map, and the periphery at the back edge.
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In Mark Antliff and Patricia Leighten, A Cubism Reader, Documents and Criticism, 1906–1914, The University of Chicago Press, 2008 > In short, he wishes to develop the visual field by multiplying it, in order > to inscribe it within the space of the canvas itself. It is at that point > that the cube will play a role, and it is there that Metzinger will use that > means to reestablish a balance that has been momentarily interrupted by > these audacious inscriptions. At the last Salon d'Automne [1910], we were > able to get an idea of that technique, inscribed and set out in simple > terms. His Femme nu, depicted from various angles and in integral > relationship with the setting, the shapes very subtly nestled one into > another, was more like a masterful demonstration of the total image than an > exclusively pictorial creation.
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Vesely presents the example of inborn conditions of blindness treated through surgery, where sight itself only emerges after a painful stage of learning, and without which, the recently acquired sense of sight would be unable to detach or recognize individual objects out of a 'visual field' (pp. 50–51). Vesely describes how the integration of the newly acquired sense relies on the fact that the world of the blind is already structured, not only in terms of temporal sequences, but spatially; and that the reconciliation of the new ability of sight takes place on an already structured ground of existing objects and spatiality. Perception such as visual or tactile is reconciled upon an implicitly structured ground. Vesely shows how the task of bridging different plateaux of representation can only be fulfilled by covering the distance to a common 'ground' (pp. 61–63).
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Phototransduction in rods and cones is somewhat unusual in that the stimulus (in this case, light) reduces the cell's response or firing rate, different from most other sensory systems in which a stimulus increases the cell's response or firing rate. This difference has important functional consequences: First, the classic (rod or cone) photoreceptor is depolarized in the dark, which means many sodium ions are flowing into the cell. Thus, the random opening or closing of sodium channels will not affect the membrane potential of the cell; only the closing of a large number of channels, through absorption of a photon, will affect it and signal that light is in the visual field. This system may have less noise relative to sensory transduction schema that increase rate of neural firing in response to stimulus, like touch and olfaction.
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This theory is supported by findings that parafoveal retinal lesions deprive a region of striate cortex of visual input, and as a result, the receptive fields of neurons near the boundary of the deprived cortical region enlarge and expand into nearby regions of the visual field. Thus, polyopia results from altered coding of contour information by neurons near the lesioned area. This mechanism offers that after a focal lesion of neurons in striate cortex, or following a retinal lesion depriving these neurons of visual input, the receptive fields of nearby healthy neurons converge to code information about contours of objects normally coded by the damaged neurons while still coding the same information about retinal location prior to the injury. This mechanism may explain why polyopia extending into a patient’s scotoma occurs following damage to primary visual cortex.
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The adenoma may be the prime causative factor behind the headache or may serve to exacerbate a headache caused by other factors. Amongst the types of headaches experienced are both chronic and episodic migraine, and more uncommonly various unilateral headaches; primary stabbing headache, short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT) \- another type of stabbing headache characterized by short stabs of pain -, cluster headache, and hemicrania continua (HS). Compressive symptoms of pituitary adenomas (visual field deficits, decreased visual acuity, headaches) are more commonly seen with macroadenomas (which are greater than 10 mm in diameter) than with microadenomas (which are less than 10 mm in diameter). Non-secreting adenomas can go undetected for an extended time because no obvious abnormalities are seen; the gradual reduction in normal activities due to decreased production of hormones is rather less evident.
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The moon looks larger near distant buildings than nearby ones in this simulated skyline The size of a viewed object can be measured objectively either as an angular size (the visual angle that it subtends at the eye, corresponding to the proportion of the visual field that it occupies), or as physical size (its real size measured in, say, meters). Perceived size is only loosely related to these concepts, however. For example, if two identical, familiar objects are placed at distances of five and ten meters, respectively, then the more distant object subtends approximately half the visual angle of the nearer object, but it is normally perceived to be the same size (a phenomenon referred to as size constancy), not as half the size. Conversely, if the more distant object did subtend the same angle as the nearer object then it is normally perceived to be twice as big.
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With an undergraduate by the name of Susan Fiske at Harvard, Taylor began a research program on salience and the effects that salience has on people's inferences. In a famous paper, Taylor and Fiske found that "point of view influences perceptions of causality, such that a person who engulfs your visual field is seen as more impactful in a situation...imagining actions from the perspective of a particular character leads to empathetic inference and recall of information best learned from that person's perspectives." Taylor also did other work on salience with regard to stereotyping and cognitive biases. For example, she found that if a person in your field is a token or solitary member of a group, they are more likely to be viewed in stereotyped role than if the person was a member of the majority group and their identity is much more salient.
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The neural basis of biased competition in human visual cortex. Neuropsychologia. 39, 1263-1276. This suppression process, according to Kastner and Ungerleider, occurs when two stimuli are presented together because they compete for neural representation, due to limited cognitive processing capacity.Kastner, S., L, G., Ungerleider. (2001). The neural basis of biased competition in human visual cortex. Neuropsychologia. 39, 1263-1276. The RF experiment suggests that as the number of objects increase, the information available for each object will decrease due to increased neural workload (suppression), and decreased cognitive capacity.Kastner, S., L, G., Ungerleider. (2001). The neural basis of biased competition in human visual cortex. Neuropsychologia. 39, 1263-1276. In order for an object in the visual field or RF be efficiently processed, there needs to be a way to bias these neurological resources towards the object. Attention prioritizes task relevant objects, biasing this process.
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As cited by: (Nonetheless two Dove prisms can be employed to rotate the visual field in experimental settings.) For cyclodeviations above 5 degrees, surgery has normally been recommended."The patient fixates a vertical line target, and the dove prism is rotated in the direction to increase the action of the insufficient muscle while fusion is maintained." Quoted from: Depending on the symptoms, the surgical correction of cyclotropia may involve a correction of an associated vertical deviation (hyper- or hypotropia), or a Harada–Ito procedure or another procedure to rotate the eye inwards, or yet another procedure to rotate it outwards.2.22 Cyclotropia: Treatment, ORBIS Telemedicine (downloaded 19 July 2013) A cyclodeviation may thus be corrected at the same time with a correction of a vertical deviation (hyper- or hypotropia); cyclodeviations without any vertical deviation can be difficult to manage surgically, as the correction of the cyclodeviation may introduce a vertical deviation.
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Visual imagery is the ability to create mental representations of things, people, and places that are absent from an individual’s visual field. This ability is crucial to problem-solving tasks, memory, and spatial reasoning.Dijkstra, N., Bosch, S. E., & van Gerven, M. A. J. “Vividness of Visual Imagery Depends on the Neural Overlap with Perception in Visual Areas”, The Journal of Neuroscience, 37(5), 1367 LP-1373. (2017). Neuroscientists have found that imagery and perception share many of the same neural substrates, or areas of the brain that function similarly during both imagery and perception, such as the visual cortex and higher visual areas. Kosslyn and colleagues (1999)Kosslyn, S. M., Pascual-Leone, A., Felician, O., Camposano, S., Keenan, J. P., L., W., … Alpert. “The Role of Area 17 in Visual Imagery: Convergent Evidence from PET and rTMS”, Science, 284(5411), 167 LP-170, (1999).
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Macknick & Martinez-Conde recorded from neurons in the lateral geniculate nucleus (LGN) and V1 V1 while presenting monoptic and dichoptic stimuli, and found that monoptic masking occurred in all the LGN and V1 neurons that were recorded, but dichoptic masking only occurred in some of the binocular neurons in V1, which supports the hypothesis that visual masking in monoptic regions is not due to feedback from dichoptic regions. This is because, if there had been feedback from higher areas of the visual field, the early circuits would have “inherited” dichoptic masking from the feedback coming from higher levels, and so would exhibit both dichoptic and monoptic masking. Although monoptic masking is stronger in the early visual areas, monoptic and dichoptic masking are equivalent in magnitude. Thus, dichoptic masking must become stronger as it proceeds down the visual hierarchy if the preceding hypothesis is correct.
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The painting becomes a meditation on the screen to the viewer. Miró's fascination for Japanese art and master SengaiGibon influenced many European and American abstract artists of the moment. The simplicity of the work of Sengai intriguing, combining geometric shapes with vertical texts caused a strong impact on Miró, who began a vocabulary of signs themselves, which Miró visual color experience the great power that supposed to make the spectator in front of three formats, a combination not only works separately, but to offer a completely new visual field that fills the viewer (TATE) There is a strong relationship between scarce resources and the dramatic impact TAT) At the time Miró painted The Hope of a Condemned Man, we find a Europe post- May 68, Protestant and unhappy, and also find that Spain looks like the dying dictatorship of General Franco. At the same time there is a Joan Miró fully recognized and also is filled with skills to find creative new ways.
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Recent research has demonstrated that the normal right hemisphere of the brain responds to melody holistically, consistent with Gestalt Psychology, whereas the left hemisphere of the brain evaluates melodic passages in a more analytic fashion, similar to the feature-detecting capacity of the left hemisphere's visual field. For instance, Regalski (1977) demonstrated that while listening to the melody of the popular carol "Silent Night", the right hemisphere thinks, "Ah, yes, Silent Night", while the left hemisphere thinks, "two sequences: the first a literal repetition, the second a repetition at different pitch levels—ah, yes, Silent Night by Franz Gruber, typical pastorate folk style." The brain for the most part works well when each hemisphere performs its own function while solving a task or problem; the two hemispheres are quite complementary. However, situations arise when the two modes are in conflict, resulting in one hemisphere interfering with the operation of the other hemisphere.
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This is a prime example that implicit memory can be less vulnerable to brain damage. A famous study investigated the Identification blindsight effect with individuals who had suffered damage to one half of the visual cortex and were blind in the opposite half of the visual field. It was discovered that when objects or pictures were shown to these blind areas, the participants said that they saw no object or picture, but a certain number were able to identify the stimulus as either a cross or circle when asked to guess at a considerably higher rate than would have been expected by chance. The reason that this happened is because the information was able to be process through the first three stages of selection, organization, and interpretation or comprehension of the perceptual cycle but failed at only the last stage of retention and memory where the identified image is entered into their awareness.
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"An Investigation of the validity, reliability, and acceptance by children of a microcomputer administration of the Peabody Picture Vocabulary Test-Revised (PPVT-R) ," As computer-human technology improves, future PPVT e-assessments research may include use of visual tracking computer interface such as wearable eye tracking glasses "Eye tracking gives Rett Syndrome patients a voice,"Davis, John (2011). "Eye- Tracking Devices Help Disabled Use Computers," so that disabled adults can respond to PPVT test items by scanning the visual field and fixing their eye gaze on the visual item they select. Future PPVT e-assessment research could integrate the human nervous system with e-administration of the PPVT. The human nervous system e-assessment would involve assessment of the P300 (P3) wave event related potential (ERP) between visual picture test items and the picture word comparing and contrasting the correct pairing of the word and picture against incorrect pairing of words and pictures.
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Egocentric vision or first-person vision is a sub-field of computer vision that entails analyzing images and videos captured by a wearable camera, which is typically worn on the head or on the chest and naturally approximates the visual field of the camera wearer. Consequently, visual data capture the part of the scene on which the user focuses to carry out the task at hand and offer a valuable perspective to understand the user's activities and their context in a naturalistic settingAn Introduction to the 3rd Workshop on Egocentric (First-person) Vision, Steve Mann, Kris M. Kitani, Yong Jae Lee, M. S. Ryoo, and Alireza Fathi, IEEE Conference on Computer Vision and Pattern Recognition Workshops 2160-7508/14, 2014, IEEE DOI 10.1109/CVPRW.2014.1338272014. The wearable camera looking forwards is often supplemented with a camera looking inward at the user's eye and able to measure a user's eye gaze, which is useful to reveal attention and to better understand the user's activity and intentions.
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Lines show path of foveal fixation during 5 seconds when the task is to memorize the situation as correctly as possible. Image fromHans-Werner Hunziker, (2006) Im Auge des Lesers: foveale und periphere Wahrnehmung – vom Buchstabieren zur Lesefreude [In the eye of the reader: foveal and peripheral perception - from letter recognition to the joy of reading] Transmedia Stäubli Verlag Zürich 2006 based on data byDE GROOT, A. : Perception and memory in chess; an experimental study of the heuristics of the professional eye. Mimeograph; Psychologisch Laboratorium Universiteit van Amsterdam, Seminarium September 1969 The distinctions between foveal (sometimes also called central) and peripheral vision are reflected in subtle physiological and anatomical differences in the visual cortex. Different visual areas contribute to the processing of visual information coming from different parts of the visual field, and a complex of visual areas located along the banks of the interhemispheric fissure (a deep groove that separates the two brain hemispheres) has been linked to peripheral vision.
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For example, Wallach & BaconWallach, H. & Bacon, J. (1977) Two kinds of adaptation in the constancy of visual direction and their different effects on the perception of shape and visual direction. Perception & Psychophysics, 21, 227–241. were able to demonstrate that two distinct processes are involved in the constancy of visual direction by showing that they adapt differently. In addition to the processes compensating for image displacements during head rotation, Wallach and various collaborators examined other sorts of compensations related to perceptual stability during bodily movement, including displacements caused by noddingWallach, H. & Bacon, J. (1976) The constancy of the orientation of the visual field. Perception & Psychophysics, 19, 492–498. and by eye movements,Wallach, H. & Lewis, C. (1966) The effect of abnormal displacement of the retinal image during eye movements. Perception & Psychophysics, 1, 25–29. Also Whipple, W. R. & Wallach, H. (1978) Direction- specific motion thresholds for abnormal image shifts during saccadic eye movement. Perception & Psychophysics, 24, 349–355.
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But in either case it is not a flat unchanging redness/blackness. Instead, if actively observed for a few minutes, one becomes aware of an apparent disorganized motion, a random field of lightness/darkness that overlays the redness/blackness of closed eyelids. For a person who tries to actively observe this closed-eye perception on a regular basis, there comes a point where if they look at a flat-shaded object with their eyes wide open, and try to actively look for this visual noise, they will become aware of it and see the random pointillistic disorganized motion as if it were a translucent overlay on top of what is actually being seen by their open eyes. When seen overlaid onto the physical world, this CEV noise does not obscure physical vision at all, and in fact is hard to notice if the visual field is highly patterned, complex, or in motion.
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Global motion is the movement of the entire image (in this case rotational) along with the circular trajectory that all the dots in the display adhere to, through rotational movement change signals can be hazed together, basically eliminating them. The motion threshold that was found to be required for silencing to take effect was 0.2 rotations per second whilst adhering to the parameters of the original experiments, and this threshold decreased as space between dots decreased, thus demonstrating the combined influence of crowding, global motion and velocity. Suchow and Alvarez explain the role that velocity has on motion silencing in that local retinotopic (of the retina) detectors fixate on specific points in the visual field, and when they are only permitted a short amount of time to process the changes occurring they do not have enough time to detect changes. The effect of velocity explains why silencing is more potent with fast motion on the retina as opposed to slow motion.
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The spatial-frequency theory refers to the theory that the visual cortex operates on a code of spatial frequency, not on the code of straight edges and lines hypothesised by Hubel and Wiesel on the basis of early experiments on V1 neurons in the cat. In support of this theory is the experimental observation that the visual cortex neurons respond even more robustly to sine-wave gratings that are placed at specific angles in their receptive fields than they do to edges or bars. Most neurons in the primary visual cortex respond best when a sine-wave grating of a particular frequency is presented at a particular angle in a particular location in the visual field. (However, as noted by Teller (1984),Teller, D. "Linking Propositions" it is probably not wise to treat the highest firing rate of a particular neuron as having a special significance with respect to its role in the perception of a particular stimulus, given that the neural code is known to be linked to relative firing rates.
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Evidently, these neurons exhibit a preference in responses to the worm configuration of moving bar stimuli and can therefore be considered feature detectors. To get a general idea of their properties, in successive experiments various rectangular dark objects of different edge lengths traverse a toad's visual field against a bright background at constant velocity; then the discharge frequency of a T5.2 neuron towards such an object is correlated with the toad's promptness of responding with prey-capture, expressed by the response latency. Thus, prey feature detection is not an all- or-nothing condition, but rather a matter of degree: the greater an object's releasing value as a prey stimulus, the stronger is prey-selective T5.2 neuron's discharge frequency, the shorter is toad's prey-catching response latency, and the higher is the number of prey-catching responses during a period of time (prey-catching activity)—as well as vice versa. Multiple unit recordings showed that a prey object activates several adjacent prey-selective neurons whose receptive fields partly overlap.
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The understanding at the single-cell level of the IT cortex and its role of utilizing memory to identify objects and or process the visual field based on color and form visual information is a relatively recent in neuroscience. Early research indicated that the cellular connections of the temporal lobe to other memory associated areas of the brain – namely the hippocampus, the amygdala, the prefrontal cortex, among others. These cellular connections have recently been found to explain unique elements of memory, suggesting that unique single-cells can be linked to specific unique types and even specific memories. Research into the single-cell understanding of the IT cortex reveals many compelling characteristics of these cells: single-cells with similar selectivity of memory are clustered together across the cortical layers of the IT cortex; the temporal lobe neurons have recently been shown to display learning behaviors and possibly relate to long-term memory; and, cortical memory within the IT cortex is likely to be enhanced over time thanks to the influence of the afferent-neurons of the medial-temporal region.
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Further research of the single-cells of the IT cortex suggests that these cells not only have a direct link to the visual system pathway but also are deliberate in the visual stimuli they respond to: in certain cases, the single-cell IT cortex neurons do not initiate responses when spots or slits, namely simple visual stimuli, are present in the visual field; however, when complicated objects are put in place, this initiates a response in the single- cell neurons of the IT cortex. This provides evidence that not only are the single-cell neurons of the IT cortex related in having a unique specific response to visual stimuli but rather that each individual single-cell neuron has a specific response to a specific stimuli. The same study also reveals how the magnitude of the response of these single-cell neurons of the IT cortex do not change due to color and size but are only influenced by the shape. This led to even more interesting observations where specific IT neurons have been linked to the recognition of faces and hands.
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A simulated vertical video frame on widescreenThe first edition of the Vertical Film Festival, projected tallscreen 9:16 aspect ratio in St Hilda's Church, Katoomba in Australia's Blue Mountains, 17 October 2014 A vertical video is a video created either by a camera or computer that is intended for viewing in portrait mode, producing an image that is taller than it is wide. It thus sits in opposition to the multiple horizontal formats normalised by cinema and television, which trace their lineage from the proscenium theatre, Western landscape painting traditions, our visual field and the plane we live on. Vertical video has historically been shunned by professional video creators because it does not fit the aspect ratio of established moving image forms, such as film and television, as well as newer web-based video players such as YouTube, meaning that black spaces appeared on either side of the image. However, the popularity of mobile video apps such as Snapchat and Periscope, which use the more mobile-friendly portrait format, have led to an increase in the production of vertical videos by advertising companies.
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The same model posed for the man in An Anniversary and Two Figures II, 1921–23, again accompanied by a young woman, here appearing more mannikin-like because of her smoothed-out hair and features and her Hawthorne stare. Once again the proximity of the figures, now bunched up on the right side of the picture, sharpens the feeling of their psychological separation from each other that their exclusion from the visual field of their partner's gaze creates. Ward suggests that this lack of interaction, the age difference, the placement of the woman behind the man and to the side of the picture, combined with the contrast between the man's depiction in color and the woman's in monochrome may signify that she is the image of a remembered love, perhaps triggered by the smell of a rose that recalls the remembered smell of one she once held (a hard-to-see stem connects it to her hand). Similarly, the strongly lit head of the old man in An Anniversary and the placement of the other figures behind him may indicate that they are people recollected from his past, seen as they were remembered.
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The different components within the category of VEPs were first described by Spehlmann in 1965 who compared human ERPs when viewing patterned and diffuse stimuli that were quickly flashed on the screen while a person was viewing the general area where the flash was to appear. However, it was not until Jeffreys and Axford (1972) that the earliest individual components of those VEPs were delineated, including the C1 component. Jeffreys and Axford had human participants view stimulus patterns of squares for a very short time (25ms), aperiodically, in different parts of the participant's visual fields while being recorded using electrodes placed towards the back of the head. Specifically, they recorded from three electrode sites placed on the longitudinal midline of the head: one 3 cm anterior to the inion (the bony projection at the posteroinferior part of the skull), and two 3 cm to either side of the midline. After averaging between like trials (trials where the stimuli were presented in the same part of the visual field) and looking at the ERPs, Jeffreys and Axford postulated that there are two distinct components in the first 150 milliseconds, the C1 and the C2.
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While some of these tasks may profit from compensation of the visual system by means of other depth cues, there are some roles for which stereopsis is imperative. Occupations requiring the precise judgment of distance sometimes include a requirement to demonstrate some level of stereopsis; in particular, there is such a requirement for airplane pilots (even if the first pilot to fly around the world alone, Wiley Post, accomplished his feat with monocular vision only.) Also surgeons normally demonstrate high stereo acuity. As to car driving, a study found a positive impact of stereopsis in specific situations at intermediate distances only; furthermore, a study on elderly persons found that glare, visual field loss, and useful field of view were significant predictors of crash involvement, whereas the elderly persons' values of visual acuity, contrast sensitivity, and stereoacuity were not associated with crashes. Binocular vision has further advantages aside from stereopsis, in particular the enhancement of vision quality through binocular summation; persons with strabismus (even those who have no double vision) have lower scores of binocular summation, and this appears to incite persons with strabismus to close one eye in visually demanding situations.
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