Some observations on visual evoked responses (VER) to dichoptic stimulation.

The possibility that the interocular depression of VER seen with dioptic stimulation, might reflect alternate suppression or binocular rivalry, unnoticed by the test subjects, was investigated in VER experiments using dichoptic stimulation with patterns of dissimilar form. Red and blue grating and checker board patterns were produced on a colour TV screen. Appropriate filtering allowed the two eyes to be stimulated separately. Provided the patterns were dissimilar enough to produce binocular rivalry, no interocular depression was noticed in the VER. The interocular depression became larger as the patterns were made similar in size and reached a maximum for patterns identical in shape. Thus the interocular depression of the VERs reported for dioptic stimulation did not seeem to be related to binocular rivalry. The results also give electrophysiological support to the notion of spartial frequency and orientation selective channels in the human visual system.