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The representation of brightness in primary visual cortex (1996)

A. F. Rossi ; C. D. Rittenhouse ; M. A. Paradiso

American Association for the Advancement of Science (AAAS)

In: Science. 273(5278): 1104-7.

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Publication Date: 1996-08-23

Description: Although neurons in primary visual cortex are sensitive to the spatial distribution and intensity of light, their responses have not been thought to correlate with the perception of brightness. Indeed, primary visual cortex is often described as an initial processing stage that sends information to higher cortical areas where perception of brightness, color, and form occurs. However, a significant percentage of neurons in primary visual cortex were shown to respond in a manner correlated with perceived brightness, rather than responding strictly to the light level in the receptive fields of the cells. This finding suggests that even at the first stage of visual cortical processing, spatial integration of information yields perceptual qualities that are only indirectly related to the pattern of illumination of the retina.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Rossi, A F -- Rittenhouse, C D -- Paradiso, M A -- New York, N.Y. -- Science. 1996 Aug 23;273(5278):1104-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Neuroscience, Brown University, Providence, RI 02912, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8688096" target="_blank"〉PubMed〈/a〉

Keywords: Animals ; Cats ; Color Perception ; *Contrast Sensitivity ; Form Perception ; Humans ; Light ; Neurons/physiology ; Visual Cortex/*physiology ; *Visual Perception

Print ISSN: 0036-8075

Electronic ISSN: 1095-9203

Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics

Published by American Association for the Advancement of Science (AAAS)

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A theory for the use of visual orientation information which exploits the columnar structure of striate cortex (1988)

Paradiso, M. A.

Springer

Biological cybernetics 58 (1988), S. 35-49

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ISSN: 1432-0770

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Computer Science , Physics

Notes: Abstract A neural model is constructed based on the structure of a visual orientation hypercolumn in mammalian striate cortex. It is then assumed that the perceived orientation of visual contours is determined by the pattern of neuronal activity across orientation columns. Using statistical estimation theory, limits on the precision of orientation estimation and discrimination are calculated. These limits are functions of single unit response properties such as orientation tuning width, response amplitude and response variability, as well as the degree of organization in the neural network. It is shown that a network of modest size, consisting of broadly orientation selective units, can reliably discriminate orientation with a precision equivalent to human performance. Of the various network parameters, the discrimination threshold depends most critically on the number of cells in the hypercolumn. The form of the dependence on cell number correctly predicts the results of psychophysical studies of orientation discrimination. The model system's performance is also consistent with psychophysical data in two situations in which human performance is not optimal. First, interference with orientation discrimination occurs when multiple stimuli activate cells in the same hypercolumn. Second, systematic errors in the estimation of orientation can occur when a stimulus is composed of intersecting lines. The results demonstrate that it is possible to relate neural activity to visual performance by an examination of the pattern of activity across orientation columns. This provides support for the hypothesis that perceived orientation is determined by the distributed pattern of neural activity. The results also encourage the view of neural activity. The results also are determined by the responses of many neurons rather than the sensitivity of individual cells.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00363954

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