Evoked potentials in man: Interaction of sound and light

Abstract

The interaction of sound and light stimuli was studied in man. Clicks followed by flashes at varying intervals were used and the EEG responses evoked by these paired stimuli in the occipital region were recorded. In contradistinction to the previously investigated paired light stimuli no refractory, supernormal (facilitation) or subnormal period was found for the first six waves (I–VI) of the second visual response. A simple superposition of the two responses was present. The origin of both responses in a common cerebral macro-structure, within the occipital region but with separate “private” projection pathways and cortical elements, is assumed. The last wave (VII) of the visual response presents a significantly smaller amplitude with click preceding the flash by 250 msec. Since the same can be seen with paired light stimuli, the origin of the waves VII evoked by click and by flash in identical cerebral structures is suggested.