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Andrew S Persichetti, Sharon L Thompson-Schill, David H Brainard, Omar H Butt, Nina S Hsu, Geoffrey K Aguirre; Application of fMRI adaptation to characterize the neural representation of color.. Journal of Vision 2012;12(9):51. doi: 10.1167/12.9.51.
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Color names may be used to divide the continuous spectrum of color percepts into discrete categories. We asked whether there is a transition from a continuous towards a categorical representation of color along the visual pathways from V1 to ventral extra-striate cortex. Ten subjects performed a behavioral color categorization task on 10 stimuli that varied along a green-blue continuum. Separately, these stimuli were presented in an fMRI experiment that employed a continuous carry-over design. The fMRI measurements were obtained while subjects performed an orthogonal attention task. Retinotopic mapping data and a chromatic vs. achromatic localizer scan were also collected.
The behavioral data revealed the expected categorization, with a transition from "green" to "blue" labels occurring in the middle of the continuum. The fMRI data were modeled for both the direct effect of a stimulus upon response as well as the adaptive effect of a given transition between stimuli. There was a recovery from adaptation within posterior visual areas that was related to the magnitude of the color stimulus transition. Within V1 and in ventral extra-striate cortex, this recovery from adaptation had a linear relationship to stimulus change. In ongoing analyses we are testing for categorical representation by examining the response to stimulus changes that cross the categorical boundary as compared to those that do not.
Meeting abstract presented at VSS 2012
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