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Dynamics of extraclassical surround modulation in three types of V1 neurons.
MedLine Citation:
PMID:  21228302     Owner:  NLM     Status:  Publisher    
Visual stimuli outside of the classical receptive field (CRF) can influence the response of neurons in primary visual cortex (V1). While recording single units in cat, we presented drifting sinusoidal gratings in circular apertures of different sizes to investigate this extraclassical surround modulation over time. For the full 2 second stimulus time course, three types of neurons were found: 1) 68% of the cells were 'suppressive'; 2) 25% were 'plateau' cells that showed response saturation with no suppression; 3) the remaining 6% of cells were 'facilitative'. Analysis of the response dynamics revealed that at response onset, activity of half of facilitative cells, 70% of plateau cells, and all suppressive cells is suppressed by the surround. However, over the next 20-30ms, surround modulation changes to stronger suppression for 'suppressive' cells, substantial facilitation for 'facilitative' cells, and weak facilitation for 'plateau' cells. For all three cell types these modulatory effects then stabilize between 100-200ms from stimulus onset. Thus, our findings illustrate two stages of surround modulation. Early modulation is mainly suppressive regardless of cell type and, because of rapid onset, may rely on feedforward mechanisms. Surround modulation that evolves later in time is not always suppressive, depending on cell type, and may be generated through different combinations of cortical circuits. Additional analysis of modulation throughout the cortical column suggests the possibility that the larger excitatory fields of 'facilitative' cells, primarily found in infragranular layers, may contribute to the second stage of suppression through intra-columnar circuitry.
Yong-Jun Liu; Maziar Hashemi-Nezhad; David C Lyon
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2011-1-12
Journal Detail:
Title:  Journal of neurophysiology     Volume:  -     ISSN:  1522-1598     ISO Abbreviation:  -     Publication Date:  2011 Jan 
Date Detail:
Created Date:  2011-1-13     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0375404     Medline TA:  J Neurophysiol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
1University of California.
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