The effect of pattern adaptation on chromatic and achromatic visual evoked potentials

Abstract

Human visual evoked potentials (VEPs) were elicited by alternately increasing and decreasing contrast by 0.1 Michelson units in the presence of an in-phase grating mask with static contrast between 0 and 0.6. Gratings were achromatic or isoluminant (R/G). Coarse achromatic gratings elicit VEPs of equal amplitude irrespective of the static contrast, like some transient-type magno-units in macaque V1. Conversely, much finer achromatic gratings elicit human VEPs, which attenuate at high static contrast reflecting nonspecific activation of sustained mechanisms. VEPs to red/green contrast increment were negative and attenuate at high-static contrast consistent with chromatic pattern adaptation of sustained parvocellular mechanisms. R/G contrast decrement elicits positive waves that are more resilient to the effects of adaptation. © 2000 John Wiley & Sons, Inc. Col Res Appl, 26, S133–S135, 2001