Color in the Cortex

We begin with a discussion of the role of human color vision, asking what value the possession of color vision adds to the perception of the natural scene, both in terms of our ability to see color differences (contrast) and in color identification. We then consider the psychophysical properties of cortical color vision and what they reveal about its use in determining shape and form. We pit against each other different models accounting for how achromatic (luminance) contrast and color contrast may be linked in the determination of shape, comparing a coloring book model, in which color plays only a subordinate or minor role, an intrinsic images model in which color contrast makes an independent contribution, and an integration model in which color and luminance contrast both provide cue-invariant form information to color–luminance shape detectors. These models are also interpreted in the light of what we know about the physiological basis of color vision through primate single cell recordings, particularly in area V1. Finally, we discuss what has been revealed about human color vision in V1 and extra striate cortex from fMRI studies.