Detection of contrary chromatic change.

In visual search experiments we examined whether targets that are distinguished from distracting items solely by a contrary change in color can be sought spatially in parallel. Targets under time-varying illumination pop out if they present a contrary luminance signal; targets under space-varying illumination can be detected in parallel when they are isoluminant. The results suggest that neurons with spatially and chromatically opposed receptive fields are active across the central visual field.