August 2012
Volume 12, Issue 9
Free
Vision Sciences Society Annual Meeting Abstract  |   August 2012
Imaging extraclassical receptive fields in early visual cortex
Author Affiliations
  • Alex R. Wade
    Department of Psychology University of York, Heslington, UK
  • B. Xiao
    Department of Brain and Cognitive Sciences, MIT
  • J. Rowland
    Department of Art Practise, UC Berkeley
Journal of Vision August 2012, Vol.12, 1395. doi:10.1167/12.9.1395
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      Alex R. Wade, B. Xiao, J. Rowland; Imaging extraclassical receptive fields in early visual cortex. Journal of Vision 2012;12(9):1395. doi: 10.1167/12.9.1395.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Psychophysically, apparent color and contrast can be modulated by long-range contextual effects. In this talk I will describe a series of neuroimaging experiments that we have performed to examine the effects of spatial context on color and contrast signals in early human visual cortex. Using fMRI we first show that regions of high contrast in the fovea exert a long-range suppressive effect across visual cortex that is consistent with a contrast gain control mechanism. This suppression is weaker when using stimuli that excite the chromatic pathways and may occur relatively early in the visual processing stream (Wade, Rowland, J Neurosci, 2010). We then used high-resolution source imaged EEG to examine the effects of context on V1 signals initiated in different chromatic and achromatic precortical pathways (Xiao and Wade, J Vision, 2010). We found that contextual effects similar to those seen in classical psychophysical ‘surround suppression’ were present in both S-cone and achromatic pathways but that there was little contextual interaction between these pathways - either in our behavioral or in our neuroimaging paradigms. Finally, we used fMRI multivariate pattern analysis techniques to examine the presence of chromatic tuning in large extraclassical receptive fields (ECRFs). We found that ECRFs have sufficient chromatic tuning to enable classification based solely on information in suppressed voxels that are not directly excited by the stimulus. In many cases, performance using ECRFs was as accurate as that using voxels driven directly by the stimulus.

Meeting abstract presented at VSS 2012

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