Abstract
Rhythmic photic stimulation ranging from 1 to 24c/sec was presented in-dependently to both eyes or to a single eye of five subjects with unilateral optic nerve affection, and the effect of monocular stimulation upon photic driving was studied. Simultaneous recordings were taken from bilateral occipital electrodes referred to a central vertex electrode. The visually evoked response (VER) to a single flash was obtained with the summation technique and discussed in relation to the mechanism of photic driving. In all subjects, driving responses were detected over two hemispheres at a wide range of stimulus frequency, when both eyes were simultaneously stimulated. The trend of the appearance of photic driving was also almost identical when the eye with intact optic nerve was independently stimulated. On the other hand, complete disappearance or marked suppression of driving was found when the eye of the side of the affected optic nerve was independently stimulated. In some cases, the primary response or the early response of the VER was markedly suppressed, while the secondary response or the late response was not changed in the response quantity. The results gave the suggestion that the primary response was essen-tial for the generation of photic driving.
