Effects of luminance on dynamic random-dot correlogram evoked visual potentials

Although dynamic random-dot correlogram evoked visual potentials (DRDC-VEPs) are a three-decade-old method to detect the cortical binocularity in humans and animals, our knowledge of the influence of fundamental stimulus parameters and the underlying cerebral processing mechanisms has remained limited. The purpose of this study was to evaluate the effect of luminance on DRDC-VEPs in adults. The variability and detectability of DRDC-VEPs were investigated under different stimulus luminance conditions with neutral density filters. Our results have demonstrated that DRDC-VEPs can be evoked in a wide luminance range, and the response amplitude was practically independent of luminance between 4.75 cd m(-2) and 0.015 cd m(-2), while DRDC-VEP latencies showed a strong linear correlation with log luminance. There is, however, a limit (0.06 cd m(-2)) below which DRDC-VEPs are not reliably recordable. Luminance reduction-induced delays in DRDC-VEP latencies cannot be explained simply by retinal mechanisms, since their regression slope does not follow the course of electroretinogram and cortical evoked potential latencies. Luminance independence of DRDC-VEP amplitude suggests that binocular correlation-processing cortical neurons receive input predominantly from the magnocellular visual pathway.