Topographic visually evoked potentials induced by stereoptic stimulus.

Topographic processes of brain activity during stereopsis were investigated by means of two different principles, with a real stereo target and a computer stereogram. Use of either principle produced the same tendency: an electrically negative focus started from the central region of the scalp and moved to the parietal and occipital regions. These flows of excitation were seen during a period of 90 to 170 ms. The difference between these two stimulus represented a return of the negative focus from the occipital pole to the parietal region in the real stereo target and a spread of the negative focus to the temporal region in the computer stereogram. Since monocular viewing of a real stereo target produces a similar visually evoked potentials wave form but with less intensity, the negative focus in binocular viewing may be due to the enhancement of binocular cells and disparity sensitive neurons in a wide area of the brain cortex. Thus stereoptic brain responses start from the central and parietal regions and move to the occipital region, making a flow of excitation.