Abstract
PURPOSE: A receptive field (RF) with center-surround S-cone antagonism (+S/−S) was posited to account for chromatic induction from patterned S-cone chromatic backgrounds (Monnier & Shevell, Nat. Neurosci., 2003). This center-surround RF implies that the amount and the direction of chromatic induction change lawfully with the size of the inducing background. This prediction was tested here. METHOD: Using an asymmetric matching task, observers set the hue, saturation and brightness of a comparison ring to match the appearance of a fixed test ring at 15cd/m2 and at a chromaticity metameric to equal-energy white (EEW). The test ring (9 min wide) was surrounded on each side by a contiguous 10cd/m2 concentric inducing ring at a chromaticity (varied between sessions) along the tritan (S-cone isolating) line from EEW. The width of the contiguous rings was varied from 0 to 34 min. The contiguous inducing rings, in turn, were surrounded by an EEW background at 10cd/m2. The diameter of the complete test field was 4 deg. RESULTS: The appearance of the test ring shifted toward the inducing chromaticity when the width of the contiguous inducing rings was less than 9 min. Increasing the width of the contiguous rings caused the appearance of the test ring to shift back toward its appearance with no contiguous inducing rings; increasing the width of the contiguous rings still further caused the color of the test to shift away from the inducing chromaticity. CONCLUSIONS: Calculations of the consequence of chromatic aberration and spread light, using the Marimont & Wandell (JOSA, 1994) method, could not account for the color shifts. The shifts in appearance with the size of the inducing rings were qualitatively consistent with a +S/−S receptive field, of the general sort recently reported in area V2 by Solomon et al (VSS 2003 Abstract). The color shifts are compared to quantitative predictions from +S/−S receptive-field organization.
This research was supported by PHS grant EY-04802.