Document Detail

Role of inhibition in the specification of orientation selectivity of cells in the cat striate cortex.
MedLine Citation:
PMID:  2487637     Owner:  NLM     Status:  MEDLINE    
Mechanisms supporting orientation selectivity of cat striate cortical cells were studied by stimulation with two superimposed sine-wave gratings of different orientations. One grating (base) generated a discharge of known amplitude which could be modified by the second grating (mask). Masks presented at nonoptimal orientations usually reduced the base-generated response, but the degree of reduction varied widely between cells. Cells with narrow orientation tuning tended to be more susceptible to mask presence than broadly tuned cells; similarly, simple cells generally showed more response reduction than did complex cells. The base and mask stimuli were drifted at different temporal frequencies which, in simple cells, permitted the identification of individual response components from each stimulus. This revealed that the reduction of the base response by the mask usually did not vary regularly with mask orientation, although response facilitation from the mask was orientation selective. In some sharply tuned simple cells, response reduction had clear local maxima near the limits of the cell's orientation-tuning function. Response reduction resulted from a nearly pure rightward shift of the response versus log contrast function. The lowest mask contrast yielding reduction was within 0.1-0.3 log unit of the lowest contrast effective for excitation. The temporal-frequency bandpass of the response-reduction mechanism resembled that of most cortical cells. The spatial-frequency bandpass was much broader than is typical for single cortical cells, spanning essentially the entire visual range of the cat. These findings are compatible with a model in which weak intrinsic orientation-selective excitation is enhanced in two stages: (1) control of threshold by nonorientation-selective inhibition that is continuously dependent on stimulus contrast; and (2) in the more narrowly tuned cells, orientation-selective inhibition that has local maxima serving to increase the slope of the orientation-tuning function.
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Visual neuroscience     Volume:  2     ISSN:  0952-5238     ISO Abbreviation:  Vis. Neurosci.     Publication Date:  1989  
Date Detail:
Created Date:  1991-03-22     Completed Date:  1991-03-22     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  8809466     Medline TA:  Vis Neurosci     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  41-55     Citation Subset:  IM; S    
Department of Electrical Engineering, Vanderbilt University, Nashville, TN 37235.
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MeSH Terms
Contrast Sensitivity
Neural Inhibition*
Perceptual Masking
Photic Stimulation
Space Perception / physiology*
Time Factors
Visual Cortex / cytology,  physiology*
Grant Support

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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