THE CORTICAL RESPONSES EVOKED BY DOUBLE PHOTIC STIMULI IN VARIOUS STATES OF MAN

Publisher Website
Google Scholar
Abstract
Visually evoked potentials were investigated in the eye-opened state and in the eye-closed state on 25 subjects. The response in the eye-opened state consists of a series of a few spikes and a subsequent prominent negative wave. The latency of the largest of the initial spikes is about 70 msec, and that of the prominent negative wave about 150 msec. The initial spike responses seem to summate, while the prominent negative waves do not show any summation. The amplitude of the prominent negative wave is greater in individuals with higher alpha voltages. The response in the eye-closed state consists of an initial negative response and a subsequent alpha-like response. The latency of the peak of the initial response is about 70 msec, and the time interval between the peaks of the initial response and of the 1st wave in the alpha-like response is about 100 msec. The latency of the peak of the prominent negative wave in the eye-opened state is not identical with that of the 1st wave in the alpha-like response in the eye-closed state. With double stimuli separated by a time interval of about 100 msec, the amplitude of the alpha-like response became greater than that calculated from 2 responses to a single stimulation. The time interval which gives the greatest amplitude response is also more restricted than that predicted from calculated responses. In the drowsy state the amplitude of the intitial response decreases and its duration is prolonged. The alpha-like response changes into irregular waves similar to theta or delta waves. Summation of the respones in the drowsy state is not observed.

This publication has 2 references indexed in Scilit: