scholarly journals Visual field representations and locations of visual areas V1/2/3 in human visual cortex

2003 ◽  
Vol 3 (10) ◽  
pp. 1 ◽  
Author(s):  
Robert F. Dougherty ◽  
Volker M. Koch ◽  
Alyssa A. Brewer ◽  
Bernd Fischer ◽  
Jan Modersitzki ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Visual Field ◽  
Human Visual Cortex ◽  
Visual Areas

scholarly journals Myelin densities in retinotopically defined dorsal visual areas of the macaque

2021 ◽  
Author(s):  
Xiaolian Li ◽  
Qi Zhu ◽  
Wim Vanduffel
Keyword(s):  
Visual Cortex ◽  
Visual Field ◽  
Cortical Thickness ◽  
New World Monkeys ◽  
Isotropic Resolution ◽  
Density Mapping ◽  
Area V2 ◽  
Visual Areas ◽  
Density Results

AbstractThe visuotopic organization of dorsal visual cortex rostral to area V2 in primates has been a longstanding source of controversy. Using sub-millimeter phase-encoded retinotopic fMRI mapping, we recently provided evidence for a surprisingly similar visuotopic organization in dorsal visual cortex of macaques compared to previously published maps in New world monkeys (Zhu and Vanduffel, Proc Natl Acad Sci USA 116:2306–2311, 2019). Although individual quadrant representations could be robustly delineated in that study, their grouping into hemifield representations remains a major challenge. Here, we combined in-vivo high-resolution myelin density mapping based on MR imaging (400 µm isotropic resolution) with fine-grained retinotopic fMRI to quantitatively compare myelin densities across retinotopically defined visual areas in macaques. Complementing previously documented differences in populational receptive-field (pRF) size and visual field signs, myelin densities of both quadrants of the dorsolateral posterior area (DLP) and area V3A are significantly different compared to dorsal and ventral area V3. Moreover, no differences in myelin density were observed between the two matching quadrants belonging to areas DLP, V3A, V1, V2 and V4, respectively. This was not the case, however, for the dorsal and ventral quadrants of area V3, which showed significant differences in MR-defined myelin densities, corroborating evidence of previous myelin staining studies. Interestingly, the pRF sizes and visual field signs of both quadrant representations in V3 are not different. Although myelin density correlates with curvature and anticorrelates with cortical thickness when measured across the entire cortex, exactly as in humans, the myelin density results in the visual areas cannot be explained by variability in cortical thickness and curvature between these areas. The present myelin density results largely support our previous model to group the two quadrants of DLP and V3A, rather than grouping DLP- with V3v into a single area VLP, or V3d with V3A+ into DM.

Pontine projection from striate and prestriate visual cortex in the macaque monkey: An anterograde study

1990 ◽  
Vol 4 (3) ◽  
pp. 205-216 ◽  
Author(s):  
W. Fries
Keyword(s):  
Visual Cortex ◽  
Visual Field ◽  
Striate Cortex ◽  
Macaque Monkey ◽  
Field Of View ◽  
Central Visual Field ◽  
Tracer Techniques ◽  
Visual Areas ◽  
Visual Cortical ◽  
Anterograde Tracer

AbstractThe projection from striate and prestriate visual cortex to the pontine nuclei has been studied in the macaque monkey by means of anterograde tracer techniques in order to assess the contribution of anatomically and functionally distinct visual cortical areas to the cortico-ponto-cerebellar loop. No projection to the pons was found from central or paracentral visual-field representations of V1 (striate cortex) or prestriate visual areas V2, and V4. Small patches of terminal labeling occurred after injections of tracer into more peripheral parts of V1, V2 and V3, and into V3A. The terminal fields were located most dorsolaterally in the anterior to middle third of the pons and were quite restricted in their rostro-caudal extent. Injections of V5, however, yielded substantial terminal labeling, stretching longitudinally throughout almost the entire pons. This projection could be demonstrated to arise from parts of V5 receiving input from central visual-field representations of striate cortex, whereas parts of V4 receiving similarly central visual-field input had no detectable projection to the pons. Its distribution may overlap to a large extent with the termination of tecto-pontine fibers and with the termination of fibers from visual areas in the medial bank (area V6 or P0) and lateral bank (area LIP) of the intraparietal sulcus, as well as from frontal eye fields (FEF). It appears that the main information relayed to the cerebellum by the visual corticopontine projection is related to movement in the field of view.

scholarly journals Seeing with Profoundly Deactivated Mid-level Visual Areas: Non-hierarchical Functioning in the Human Visual Cortex

2008 ◽  
Vol 19 (7) ◽  
pp. 1687-1703 ◽  
Author(s):  
Sharon Gilaie-Dotan ◽  
Anat Perry ◽  
Yoram Bonneh ◽  
Rafael Malach ◽  
Shlomo Bentin
Keyword(s):  
Visual Cortex ◽  
Human Visual Cortex ◽  
Visual Areas

scholarly journals Masking Disrupts Reentrant Processing in Human Visual Cortex

2007 ◽  
Vol 19 (9) ◽  
pp. 1488-1497 ◽  
Author(s):  
J. J. Fahrenfort ◽  
H. S. Scholte ◽  
V. A. F. Lamme
Keyword(s):  
Visual Cortex ◽  
Current Source ◽  
Visual Awareness ◽  
Human Visual Cortex ◽  
Density Maps ◽  
Visual Areas ◽  
Ground Segmentation ◽  
Feedback Connections ◽  
Subject Performance ◽  
Reentrant Processing

In masking, a stimulus is rendered invisible through the presentation of a second stimulus shortly after the first. Over the years, authors have typically explained masking by postulating some early disruption process. In these feedforward-type explanations, the mask somehow “catches up” with the target stimulus, disrupting its processing either through lateral or interchannel inhibition. However, studies from recent years indicate that visual perception—and most notably visual awareness itself—may depend strongly on cortico-cortical feedback connections from higher to lower visual areas. This has led some researchers to propose that masking derives its effectiveness from selectively interrupting these reentrant processes. In this experiment, we used electroencephalogram measurements to determine what happens in the human visual cortex during detection of a texture-defined square under nonmasked (seen) and masked (unseen) conditions. Electro-encephalogram derivatives that are typically associated with reentrant processing turn out to be absent in the masked condition. Moreover, extrastriate visual areas are still activated early on by both seen and unseen stimuli, as shown by scalp surface Laplacian current source-density maps. This conclusively shows that feedforward processing is preserved, even when subject performance is at chance as determined by objective measures. From these results, we conclude that masking derives its effectiveness, at least partly, from disrupting reentrant processing, thereby interfering with the neural mechanisms of figure-ground segmentation and visual awareness itself.

Residual Vision in a Subject with Damaged Visual Cortex

1999 ◽  
Vol 11 (5) ◽  
pp. 502-510 ◽  
Author(s):  
Heinz Schärli ◽  
Alison M. Harman ◽  
John H. Hogben
Keyword(s):  
Visual Cortex ◽  
Visual Field ◽  
Target Stimulus ◽  
Striate Cortex ◽  
Light Flash ◽  
Black And White ◽  
Confidence Levels ◽  
Residual Vision ◽  
Visual Areas ◽  
The Subject

It is well known that a lesion in the optic radiation or striate cortex leads to blind visual regions in the retinotopically corresponding portion of the visual field. However, various studies show that some subjects still perceive certain stimuli even when presented in the “blind” visual field. Such subjects either perceive stimuli abnormally or only certain aspects of them (residual vision) or, in some cases, deny perception altogether even though visual performance can be shown to be above chance (blindsight). Research on monkeys has suggested a variety of parallel extrastriate visual pathways that could bypass the striate cortex and mediate residual vision or blindsight. In the present study, we investigated a subject with perimetrically blind visual areas caused by bilateral brain damage. Black and white stimuli were presented at many locations in the intact and affected areas of the visual field. The subject's task was to state, using confidence levels, whether the target stimulus was black or white. The results revealed an area in the “blind” visual field in which the subject perceived a light flash when the experimental black stimulus was presented. We hypothesize that a spared region in the visual cortex most likely accounts for these findings.

Visual Field Maps of the Human Visual Cortex for Central and Peripheral Vision

2014 ◽  
Vol 1 (2) ◽  
pp. 102-110 ◽  
Author(s):  
Bin Wang ◽  
Hiroki Yamamoto ◽  
Jinglong Wu ◽  
Yoshimichi Ejima
Keyword(s):  
Visual Cortex ◽  
Visual Field ◽  
Peripheral Vision ◽  
Human Visual Cortex ◽  
Visual Field Maps

scholarly journals Enhanced attentional gain as a mechanism for generalized perceptual learning in human visual cortex

2014 ◽  
Vol 112 (5) ◽  
pp. 1217-1227 ◽  
Author(s):  
Anna Byers ◽  
John T. Serences
Keyword(s):  
Visual Cortex ◽  
Perceptual Learning ◽  
Broad Class ◽  
Sensory Information ◽  
Large Set ◽  
Human Visual Cortex ◽  
Visual Areas ◽  
Early Visual Cortex ◽  
Response Profiles ◽  
Sensory Responses

Learning to better discriminate a specific visual feature (i.e., a specific orientation in a specific region of space) has been associated with plasticity in early visual areas ( sensory modulation) and with improvements in the transmission of sensory information from early visual areas to downstream sensorimotor and decision regions ( enhanced readout). However, in many real-world scenarios that require perceptual expertise, observers need to efficiently process numerous exemplars from a broad stimulus class as opposed to just a single stimulus feature. Some previous data suggest that perceptual learning leads to highly specific neural modulations that support the discrimination of specific trained features. However, the extent to which perceptual learning acts to improve the discriminability of a broad class of stimuli via the modulation of sensory responses in human visual cortex remains largely unknown. Here, we used functional MRI and a multivariate analysis method to reconstruct orientation-selective response profiles based on activation patterns in the early visual cortex before and after subjects learned to discriminate small offsets in a set of grating stimuli that were rendered in one of nine possible orientations. Behavioral performance improved across 10 training sessions, and there was a training-related increase in the amplitude of orientation-selective response profiles in V1, V2, and V3 when orientation was task relevant compared with when it was task irrelevant. These results suggest that generalized perceptual learning can lead to modified responses in the early visual cortex in a manner that is suitable for supporting improved discriminability of stimuli drawn from a large set of exemplars.

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