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Combinatorial representation of color in visual cortex
Terry Sejnowski,1 Thomas Wachtler,2 Tom
Albright,1 and Javier Movellan3
1Salk Institute
2University of Freiburg
3UCSD
The responses of many neurons in primary visual cortex of monkeys are
selective for the color of homogeneous color patches in their
receptive fields presented on a neutral gray background. When stimuli
were presented on colored backgrounds, chromatic tuning was different
in most neurons, and the changes in the tuning curves depended on the
chromatic contrast between stimulus and background. Although the
response tuning curves and their modulation by the background color do
not appear to be separable, the likelihood of the ratio of spike
counts can be fit by a product of two terms one of which depends only
on the color in the receptive field and the second only on the color
in the nonclassical receptive field. This type of separability may be
a general mechanism that the cortex uses to combine information from
different contexts.