The relation between the photic driving of EEG and the response evoked by photic stimulation in man.

The human EEG can be driven by rhythmic photic stimulation with a frequency of about 10 cps. This has been known for some time (WALTER 1953). On the other hand, the relation between the visually evoked potential and the driving of the EEG has remained obscure because of the difficulty of obtaining the evoked potential from the human scalp . With the development of the averaging technique the recording and analysis of the visually evoked potential has become possible (CoBB and DAWSON 1960). A rhythmic after discharge has already been described in man (BARLOW and BRAZIER 1957, CIGANEK 1961, HRBEK and MARES 1964) and the relation between the early component of the evoked response and the alpha waves of the EEG has been investigated (Kooi and BAGCHI 1964). In a previous paper from our laboratory we found that the rhythmic after-discharge showed summation and that there was a tendency for these alpha-like waves resulting from photic stimulation to be synchronized by double stimuli with intervals of about 100 msec (KITASATO and HATSUDA 1966). The purpose of this present experiment is to investigate the relation between the photic driving of the EEG and these alpha-like waves in the evoked potential. With multiple stimulation I could find the clear relation between the photic driving and these alpha-like waves .