TEMPORAL RESPONSE CHARACTERISTICS OF THE SPATIOCHROMATIC VISUAL-EVOKED POTENTIAL - NONLINEARITIES AND DEPARTURES FROM PSYCHOPHYSICS

Although the visual evoked potential (VEP) for isoluminant stimuli has been characterized in terms of spatiochromatic parameters, temporal t uning along various chromatic directions has received less systematic attention. Additionally, there has been little categorical comparison of psychophysical appearance with VEP responses obtained for temporal variation of these patterns. At appropriate contrasts the VEE's for co lor axes (LM, S) show a robust and contrast-sensitive temporal tuning peak at 4 Hz. Contrast response functions at 4 Hz for the LM color axi s are markedly nonmonotonic. However, there is a clear monotonicity wi th contrast for VEP latencies along these color axes. The anomalous be havior does not appear to be due to interactions between chromatic sig nals, to luminance artifact, or to rod intrusion. These anomalies in t he temporal characteristics of the chromatic VEP may reflect interacti ons between chromatic responses and inherent cortical responsivity not linked to psychophysical behavior. (C) 1997 Optical Society of Americ a.