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Abstract:
Extrastriate visual area V4 is thought to play an important role in color processing. To study how color and luminance affect activity of V4 neurons, we decomposed colored natural images (I) into chrominance (C) and luminance (L) parts, such that the images can be reconstructed as the sum of these two contributions (i. e. I=L+C). In addition, we also studied their response to grayscale versions of the colored natural image stimuli. We have preliminary data from 82 V4 neurons. We used eight natural images as stimuli, which were 10 by 10 deg in size and presented for 300ms while monkeys were maintaining central fixation. Average neural activity was similar for colored and black white versions of the natural image stimuli, while luminance (L) and chrominance (C) contributions elicited greater and less average activity, respectively. Analysis of neural selectivity revealed that V4 neurons were on average significantly more selective for colored than black white natural images, and that selectivity for both the L and C components of these images was significantly lower. These results help clarify the importance of color for neural activity in extrastriate visual cortex.
