Supplementary Figure 2: a, Activation maps showing responses to color versus responses to black-and-white using colors 7 & 8 (a) and colors 1-6 and 9-12 (b) in M1 (left) and M2 (right).

The bottom row in (a) and b shows the 20° ventral rotated view corresponding to Figure 3a. Colors 7 and 8 are the two colors least likely to be contaminated by luminance artifacts (see text). (c) Color-biased regions identified by comparing responses to all colors besides colors 7 & 8 versus responses to achromatic gratings, using no spatial smoothing, in M1. Bottom set of panels shows expanded view of early retinotopic cortex, showing comparable pattern of activation to that described by Conway et al. (2007). Note the luminance bias within V3, and the suggestion of a stripe pattern within V2, presumably reflecting the concentration of color cells within the cytochrome-oxidase thin stripes. Unlike the earlier report, color stimuli were calibrated using the DKL color space, and the saturation of the achromatic gratings was adjusted so that V1 gave the same magnitude of response to the achromatic gratings as it gave to colors 7&8. This calibration procedure was effective, as shown by the lack of a color bias in V1.