Representation of Hue and Saturation of Color in the Visual Cortex of the Monkey

Abstract

We can summarize the transformation of color signals in the early stages as follows. First, color is represented by the relative activities of three types of cone photoreceptors. Secondly, linear combination of cone signals occurs in regular manners and color is represented by two axes, namely L–M and S axes (two-axes representation). Finally, signals tuned to various directions in the chromaticity diagram starts to be formed in V1 resulting in hue selective neurons as well as neurons selective for saturation. We can call this third stage as having “multi-axes representation of color”. Color representation based on hue and saturation seems a principle way ubiquitous across different areas in the cortical visual areas.