A central mechanism of chromatic contrast

The color appearance of a light can be altered by introducing a second, sur rounding field. This phenomenon, called chromatic induction, is attenuated by chromatic variation within a remote region outside the surround [Shevell & Wei (1998). Vision Research, 38, 1561-1566]. We now consider the locus o f the neural mechanism mediating the attenuation caused by the remote chrom atic contrast. In the first experiment, the magnitude of chromatic variatio n within the remote region is changed either: (i) in the same eye that view s the patch judged in color; or (ii) in only the opposite eye. The measurem ents are virtually the same in both cases, which implies attenuation of chr omatic induction is mediated by a central, binocular mechanism. In the seco nd experiment, the patch with its immediate inducing surround is changed in binocular disparity relative to the remote region with chromatic variation . The patch and surround, seen together in one depth plane, are perceived t o be in front of, behind, or in the same plane as the remote region with ch romatic variation. Attenuation of chromatic induction is strongest when the patch and surround are in the same depth plane as the remote region. This change of color appearance with disparity is consistent with a central bino cular process. Overall, the color-appearance measurements are explained by monocular encoding of chromatic differences at edges, and a central binocul ar mechanism of chromatic-contrast gain control. (C) 2000 Elsevier Science Ltd. All rights reserved.