Functional organization for color and orientation in macaque V4

Visual area V4 in the macaque monkey is a cortical area strongly involved in shape and color perception. However, fundamental questions about V4 are still debated. V4 was initially characterized as a color processing area but subsequent studies revealed that it contains a diverse complement of cells, including those with preference for color, orientation, disparity, as well as higher order feature preferences. This has led to disputes and uncertainty about the role of V4 in vision. In this study, using intrinsic signal optical imaging methods in awake, behaving monkeys, we demonstrate functional organization for different feature preferences within V4. Optical images reveal that regions with preferential response to color or luminance are largely separate from orientation selective regions. These results help resolve long-standing controversies regarding functional diversity and retinotopy within V4 and indicate the presence of spatially biased distribution of featural representation in V4 in the ventral visual pathway.