Contrast adaptation reveals increased organizational complexity of chromatic processing in the visual evoked potential

Abstract

Results from psychophysics and single-unit recordings suggest that color vision comprises multiple stages of processing. Post-receptoral channels appear to consist of both a stage of broadly-tuned opponent channels that compare cone signals, and a subsequent stage, which includes cells tuned to many different directions in color space. The chromatic visual evoked potential (crVEP) has demonstrated chromatic processing selective for cardinal axes of color space. However, crVEP evidence for higher-order color mechanisms is lacking. The present study aimed to assess the contribution of lower and higher order color mechanisms to the chromatic VEP by using chromatic contrast adaptation. The results revealed the presence of mechanisms tuned to intermediate directions in color space in addition to those tuned to the fundamental cardinal axes.