Investigating the Steady State Visually Evoked Cortical Response

Abstract

Steady state visually evoked cortical responses were obtained by sinusoidally modulating fluorescent lights. Sums of sine waves with a frequency range of 5.5 Hz to 49 Hz were presented simultaneously to subjects to allow a control theoretic examination of the describing function of the EEG response. Subjects observed the stimulus in a “lights only” condition and were also tested viewing the flickering lights while doing a video decision task presented in the same field. Results indicate that reconstruction of the describing function across several frequencies was consistent for replications of each condition. Differences between the decision condition and lights only were observed around 9.5 Hz to 11.5 Hz. Frequency dependent sensitivity to the evoking stimulus was observed, and individual differences were indicated in frequency sensitivity to the evoking stimuli.