The Effects of the Intensity of Photic Stimulation on Cortical Evoked Potentials in Arousal and during Sleep

Abstract

In the scotopic stage, the influences of intensity of stimulating light on the cortical evoked potential were studied in both arousal and sleep. The potential was recorded by means of the super imposition method of Dawson. Stimulating light was from Xenon lamp, white, 50[mu] sec. in duration and 0.3 Joule/sec, in electric energy. Light source was in the distance of 30 cm in front of the eyes of the subjects. In arousal, the changes of the evoked potentials following the reduction of the intensity of stimulating light were categorized into three types, i.e. delay of culmination time, decreasing of amplitudes and shifting of the prominent component. During sleep, although the amplitude of the response was far higher than in arousal, the threshold to the stimulating light increased to over 103 fold that during arousal.