Inhibitory binocular interaction in human vision and a possible mechanism subserving stereoscopic fusion

Abstract

IN the human visual system, pathways from the two eyes converge anatomically by partial crossing over of the optic nerve fibres at the optic chiasma. Neurophysiological studies of the primary visual cortex of primates have established that these converging pathways carry signals from both eyes to the same cortical neurones¹. In normal viewing conditions, each eye forms an image of the external visual field, the point of attention in the field being centrally fixated in both eyes. There is a small difference in the relative positions of non-central image points formed on the two retinae because the eyes view the visual field from slightly different positions. The ability of the primate visual system to extract information about the depth of a focused object in the visual field apparently rests on the convergence on to single cortical neurones of signals arising from the slightly displaced images in the two eyes². If each eye perceives a totally different visual stimulus, however, the visual signals arising from the two stimuli are perceptually antagonistic and, in this situation, an observer usually detects only one stimulus at a time. This phenomenon is referred to as binocular rivalry. We have investigated interactions between visual signals produced by two different stimuli when presented one to each eye.