Document Detail

Motion selectivity and the contrast-response function of simple cells in the visual cortex.
MedLine Citation:
PMID:  1772804     Owner:  NLM     Status:  MEDLINE    
The responses of simple cells were recorded from the visual cortex of cats, as a function of the position and contrast of counterphase and drifting grating patterns, to assess whether direction selectivity can be accounted for on the basis of linear summation. The expected responses to a counterphase grating, given a strictly linear model, would be the sum of the responses to the two drifting components. The measured responses were not consistent with the linear prediction. For example, nearly all cells showed two positions where the responses approached zero (i.e. two "null phase positions"); this was true, even for the most direction selective cells. However, the measured responses were consistent with the hypothesis that direction selectivity is a consequence of the linear spatiotemporal receptive-field structure, coupled with the nonlinearities revealed by the contrast-response function: contrast gain control, halfwave rectification, and expansive exponent. When arranged in a particular sequence, each of these linear and nonlinear mechanisms performs a useful function in a general model of simple cells. The linear spatiotemporal receptive field initiates stimulus selectivity (for direction, orientation, spatial frequency, etc.). The expansive response exponent enhances selectivity. The contrast-set gain control maintains selectivity (over a wide range of contrasts, in spite of the limited dynamic response range and steep slope of the contrast-response function). Rectification conserves metabolic energy.
D G Albrecht; W S Geisler
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Visual neuroscience     Volume:  7     ISSN:  0952-5238     ISO Abbreviation:  Vis. Neurosci.     Publication Date:  1991 Dec 
Date Detail:
Created Date:  1992-03-05     Completed Date:  1992-03-05     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  8809466     Medline TA:  Vis Neurosci     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  531-46     Citation Subset:  IM; S    
Department of Psychology, University of Texas, Austin 78712.
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MeSH Terms
Contrast Sensitivity / physiology*
Linear Models
Motion Perception / physiology*
Pattern Recognition, Visual
Visual Cortex / cytology,  physiology*
Grant Support

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