The Experts below are selected from a list of 141 Experts worldwide ranked by ideXlab platform
Charles G. Gross - One of the best experts on this subject based on the ideXlab platform.
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Direction of motion discrimination after early lesions of Striate Cortex (V1) of the macaque monkey
Proceedings of the National Academy of Sciences of the United States of America, 2001Co-Authors: Tirin Moore, Hillary R Rodman, Charles G. GrossAbstract:Abstract Previous studies have established that humans and monkeys with damage to Striate Cortex are able to detect and localize bright targets within the resultant scotoma. Electrophysiological evidence in monkeys suggests that residual vision also might include sensitivity to direction of visual motion. We tested whether macaque monkeys with longstanding lesions of Striate Cortex (V1), sustained in infancy, could discriminate visual stimuli on the basis of direction of motion. Three monkeys with unilateral Striate Cortex lesions sustained in infancy were tested 2–5 years postlesion on a direction of motion discrimination task. Each monkey was trained to make saccadic eye movements to a field of moving dots or to withhold such eye movements, depending on the direction of motion in a coherent random dot display. With smaller motion displays, monkeys were unable to detect or discriminate motion within the scotoma, although they could discriminate moving from static stimuli. Yet, each monkey was able to discriminate direction of motion when the motion stimulus was larger, but still confined to the scotoma. The results demonstrate that the recovery after infant damage to Striate Cortex includes some sensitivity to direction of visual motion.
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Greater residual vision in monkeys after Striate Cortex damage in infancy.
Journal of neurophysiology, 1996Co-Authors: Tirin Moore, Charles G. Gross, Hillary R Rodman, A. B. Repp, R. S. MezrichAbstract:1. Monkeys with large unilateral surgical ablations of Striate Cortex, sustained either in adulthood or at 5–6 wk of age, were trained on an oculomotor detection and localization task and tested wi...
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localization of visual stimuli after Striate Cortex damage in monkeys parallels with human blindsight
Proceedings of the National Academy of Sciences of the United States of America, 1995Co-Authors: Tirin Moore, Hillary R Rodman, Allen B Repp, Charles G. GrossAbstract:Blindsight is a phenomenon in which human patients with damage to Striate Cortex deny any visual sensation in the resultant visual field defect but can nonetheless detect and localize stimuli when persuaded to guess. Although monkeys with Striate lesions have also been shown to exhibit some residual vision, it is not yet clear to what extent the residual capacities in monkeys parallel the phenomenon of human blindsight. To clarify this issue, we trained two monkeys with unilateral lesions of Striate Cortex to make saccadic eye movements to visual targets in both hemifields under two conditions. In the condition analogous to clinical perimetry, they failed to initiate saccades to targets presented in the contralateral hemifield and thus appeared "blind." Only in the condition where the fixation point was turned off simultaneously with the onset of the target--signaling the animal to respond at the appropriate time--were monkeys able to localize targets contralateral to the Striate lesion. These results indicate that the conditions under which residual vision is demonstrable are similar for monkeys with Striate Cortex damage and humans with blindsight.
Tirin Moore - One of the best experts on this subject based on the ideXlab platform.
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Direction of motion discrimination after early lesions of Striate Cortex (V1) of the macaque monkey
Proceedings of the National Academy of Sciences of the United States of America, 2001Co-Authors: Tirin Moore, Hillary R Rodman, Charles G. GrossAbstract:Abstract Previous studies have established that humans and monkeys with damage to Striate Cortex are able to detect and localize bright targets within the resultant scotoma. Electrophysiological evidence in monkeys suggests that residual vision also might include sensitivity to direction of visual motion. We tested whether macaque monkeys with longstanding lesions of Striate Cortex (V1), sustained in infancy, could discriminate visual stimuli on the basis of direction of motion. Three monkeys with unilateral Striate Cortex lesions sustained in infancy were tested 2–5 years postlesion on a direction of motion discrimination task. Each monkey was trained to make saccadic eye movements to a field of moving dots or to withhold such eye movements, depending on the direction of motion in a coherent random dot display. With smaller motion displays, monkeys were unable to detect or discriminate motion within the scotoma, although they could discriminate moving from static stimuli. Yet, each monkey was able to discriminate direction of motion when the motion stimulus was larger, but still confined to the scotoma. The results demonstrate that the recovery after infant damage to Striate Cortex includes some sensitivity to direction of visual motion.
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Greater residual vision in monkeys after Striate Cortex damage in infancy.
Journal of neurophysiology, 1996Co-Authors: Tirin Moore, Charles G. Gross, Hillary R Rodman, A. B. Repp, R. S. MezrichAbstract:1. Monkeys with large unilateral surgical ablations of Striate Cortex, sustained either in adulthood or at 5–6 wk of age, were trained on an oculomotor detection and localization task and tested wi...
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localization of visual stimuli after Striate Cortex damage in monkeys parallels with human blindsight
Proceedings of the National Academy of Sciences of the United States of America, 1995Co-Authors: Tirin Moore, Hillary R Rodman, Allen B Repp, Charles G. GrossAbstract:Blindsight is a phenomenon in which human patients with damage to Striate Cortex deny any visual sensation in the resultant visual field defect but can nonetheless detect and localize stimuli when persuaded to guess. Although monkeys with Striate lesions have also been shown to exhibit some residual vision, it is not yet clear to what extent the residual capacities in monkeys parallel the phenomenon of human blindsight. To clarify this issue, we trained two monkeys with unilateral lesions of Striate Cortex to make saccadic eye movements to visual targets in both hemifields under two conditions. In the condition analogous to clinical perimetry, they failed to initiate saccades to targets presented in the contralateral hemifield and thus appeared "blind." Only in the condition where the fixation point was turned off simultaneously with the onset of the target--signaling the animal to respond at the appropriate time--were monkeys able to localize targets contralateral to the Striate lesion. These results indicate that the conditions under which residual vision is demonstrable are similar for monkeys with Striate Cortex damage and humans with blindsight.
Alan Cowey - One of the best experts on this subject based on the ideXlab platform.
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Striate Cortex v1 activity gates awareness of motion
Nature Neuroscience, 2005Co-Authors: Juha Silvanto, Alan Cowey, Nilli Lavie, Vincent WalshAbstract:A key question in understanding visual awareness is whether any single cortical area is indispensable. In a transcranial magnetic stimulation experiment, we show that observers' awareness of activity in extraStriate area V5 depends on the amount of activity in Striate Cortex (V1). From the timing and pattern of effects, we infer that back-projections from extraStriate Cortex influence information content in V1, but it is V1 that determines whether that information reaches awareness.
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Defensive responses to looming visual stimuli in monkeys with unilateral Striate Cortex ablation.
Neuropsychologia, 1992Co-Authors: Sheila M. King, Alan CoweyAbstract:Abstract A number of residual visual functions including detection, localization and discrimination of visual stimuli, have been demonstrated in the “blind” fields of monkeys and human patients following damage to Striate Cortex. We report here that avoidance movements of the head can also be elicited from monkeys with unilateral Striate Cortex ablations when a “looming” stimulus is presented within the hemianopic and presumably “blind” field. The possible role of the retinofugal projection to superior colliculus in the mediation of these defensive head movements is discussed.
Hillary R Rodman - One of the best experts on this subject based on the ideXlab platform.
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Direction of motion discrimination after early lesions of Striate Cortex (V1) of the macaque monkey
Proceedings of the National Academy of Sciences of the United States of America, 2001Co-Authors: Tirin Moore, Hillary R Rodman, Charles G. GrossAbstract:Abstract Previous studies have established that humans and monkeys with damage to Striate Cortex are able to detect and localize bright targets within the resultant scotoma. Electrophysiological evidence in monkeys suggests that residual vision also might include sensitivity to direction of visual motion. We tested whether macaque monkeys with longstanding lesions of Striate Cortex (V1), sustained in infancy, could discriminate visual stimuli on the basis of direction of motion. Three monkeys with unilateral Striate Cortex lesions sustained in infancy were tested 2–5 years postlesion on a direction of motion discrimination task. Each monkey was trained to make saccadic eye movements to a field of moving dots or to withhold such eye movements, depending on the direction of motion in a coherent random dot display. With smaller motion displays, monkeys were unable to detect or discriminate motion within the scotoma, although they could discriminate moving from static stimuli. Yet, each monkey was able to discriminate direction of motion when the motion stimulus was larger, but still confined to the scotoma. The results demonstrate that the recovery after infant damage to Striate Cortex includes some sensitivity to direction of visual motion.
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Greater residual vision in monkeys after Striate Cortex damage in infancy.
Journal of neurophysiology, 1996Co-Authors: Tirin Moore, Charles G. Gross, Hillary R Rodman, A. B. Repp, R. S. MezrichAbstract:1. Monkeys with large unilateral surgical ablations of Striate Cortex, sustained either in adulthood or at 5–6 wk of age, were trained on an oculomotor detection and localization task and tested wi...
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localization of visual stimuli after Striate Cortex damage in monkeys parallels with human blindsight
Proceedings of the National Academy of Sciences of the United States of America, 1995Co-Authors: Tirin Moore, Hillary R Rodman, Allen B Repp, Charles G. GrossAbstract:Blindsight is a phenomenon in which human patients with damage to Striate Cortex deny any visual sensation in the resultant visual field defect but can nonetheless detect and localize stimuli when persuaded to guess. Although monkeys with Striate lesions have also been shown to exhibit some residual vision, it is not yet clear to what extent the residual capacities in monkeys parallel the phenomenon of human blindsight. To clarify this issue, we trained two monkeys with unilateral lesions of Striate Cortex to make saccadic eye movements to visual targets in both hemifields under two conditions. In the condition analogous to clinical perimetry, they failed to initiate saccades to targets presented in the contralateral hemifield and thus appeared "blind." Only in the condition where the fixation point was turned off simultaneously with the onset of the target--signaling the animal to respond at the appropriate time--were monkeys able to localize targets contralateral to the Striate lesion. These results indicate that the conditions under which residual vision is demonstrable are similar for monkeys with Striate Cortex damage and humans with blindsight.
Jonathan C. Horton - One of the best experts on this subject based on the ideXlab platform.
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Striate Cortex Functions
2012Co-Authors: Daniel L. Adams, Jonathan C. HortonAbstract:Definition Striate Cortex is the primary sensory cortical area for vision. Damage to Striate Cortex causes blind regions, called scotomas, in the field of vision. Striate Cortex derives its name from the stria of ▶Gennari, a prominent band of ▶myelin in layer 4, visible to the naked eye. In histological sections, Striate Cortex has a characteristic laminar cell structure (Fig. 1). Striate Cortex is located within the calcarine sulcus on the medial face of each ▶occipital lobe. It occupies about 10% of the whole cerebral Cortex. Each neuron in Striate Cortex responds to visual stimuli presented within a small portion of the visual field, known as the ▶receptive field (▶Visual cortical and subcortical receptive fields). The properties of a visual cell can be ascertained by analyzing the response to different types of visual stimuli falling within the receptive field. Thus, the functions of Striate Cortex can be defined by identifying the cardinal properties of its constituent cells, such as selectivity for stimulus orientation, direction of motion and stereoscopic depth (▶Binocular Vision). These properties must be synthesized within Striate Cortex, because they are not present in the cells that provide ascending input. Another way to define the functions of Striate Cortex is to examine how the properties of single cells are related to anatomical structures, commonly revealed by the presence of functional maps. Neurons with similar properties tend to be grouped together, and there is a continuous and gradual change in physiological characteristics across the cortical sheet. Numerous superimposed maps are present within area V1 that together provide full coverage of the visual field for multiple visual modalities.
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Labeling of cytochrome oxidase patches in intact flatmounts of Striate Cortex.
Journal of neuroscience methods, 2005Co-Authors: John R. Economides, Jonathan C. HortonAbstract:Primate Striate Cortex contains a prominent system of columns referred to as cytochrome oxidase (CO) patches. Studies directed at the morphology and interconnections of cells in patches would be facilitated by a method that revealed the location of patches in the intact Cortex. In three adult rhesus monkeys we prepared flatmounts of Striate Cortex [Horton JC, Hocking DR. Intrinsic variability of ocular dominance column periodicity in normal macaque monkeys. J Neurosci 1996;16:7228-39; Sincich LC, Adams DL, Horton JC. Complete flatmounting of the macaque cerebral Cortex. Vis Neurosci 2003;20:663-86]. The flattened specimens were then reacted for CO activity prior to sectioning. Transillumination of the intact cortical sheet revealed an extensive pattern of dark ovals. It was confirmed that this pattern corresponded to the CO patches by subsequently cutting tangential sections and comparing them with images from the intact block. In vitro labeling of CO patches in the intact Striate Cortex may prove useful for directing injections of anatomical tracers such as Lucifer Yellow or DiI into identified patch and interpatch compartments.
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Pattern of ocular dominance columns in human Striate Cortex in strabismic amblyopia
Visual Neuroscience, 1996Co-Authors: Jonathan C. Horton, Davina R. HockingAbstract:Previous experiments in animals have shown that early unilateral eyelid suture, a model of amblyopia induced by cataract, causes shrinkage of ocular dominance columns serving the deprived eye in the Striate Cortex. It is unknown whether the ocular dominance columns are affected in amblyopia produced by strabismus. We examined specimens of Striate Cortex obtained postmortem from a 79-year-old woman with a history of amblyopia in her left eye (20/800) since age 2 from accommodative esotropia. Four years prior to her death, she suffered an ischemic infarct of the left optic disc. This injury to the left optic disc made it possible to label the ocular dominance columns using cytochrome oxidase histochemistry. The pattern of ocular dominance columns was reconstructed throughout most of the right Striate Cortex. No shrinkage of columns was found. In the left Cortex only half the column mosaic was labelled, because the patient had some residual vision in the temporal retina of her left eye. The columns within the labelled portion of the overall mosaic appeared normal. These findings indicate that shrinkage of ocular dominance columns does not occur in humans with amblyopia caused by accommodative esotropia. The ocular dominance columns are probably no longer susceptible to shrinkage at the age when most children with this condition begin to develop amblyopia.
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The representation of the visual field in human Striate Cortex : a revision of the classic Holmes map
Archives of Ophthalmology, 1991Co-Authors: Jonathan C. Horton, W F HoytAbstract:• We have tested the accuracy of Gordon Holmes' retinotopic map of human Striate Cortex by correlating magnetic resonance scans with homonymous field defects in patients with clearly defined occipital lobe lesions. Our findings indicate that Holmes underestimated the cortical magnification of central vision. In a revised map of the human Striate Cortex, we expand the area subserving central vision and reduce the area devoted to peripheral vision. These changes bring the map of human Striate Cortex into agreement with data reported for closely related nonhuman primate species.
