Search for color 'center(s)' in macaque visual cortex.

It is often stated that color is selectively processed in cortical area V4, in both macaques and humans. However most recent data suggests that color is instead processed in region(s) antero-ventral to V4. Here we tested these two hypotheses in macaque visual cortex, where 'V4' was originally defined, and first described as color selective. Activity produced by equiluminant color-varying (versus luminance-varying) gratings was measured using double-label deoxyglucose in awake fixating macaques, in multiple areas of flattened visual cortex. Much of cortex was activated near-equally by both color- and luminance-varying stimuli. In remaining cortical regions, discrete color-biased columns were found in many cortical visual areas, whereas luminance-biased activity was found in only a few specific regions (V1 layer 4B and area MT). Consistent with a recent hypothesis, V4 was not uniquely specialized for color processing, but areas located antero-ventral to V4 (in/near TEO and anterior TE) showed more color-biased activity.