VISUAL EVOKED RESPONSES IN SUBJECTS TRAINED TO CONTROL ALPHA RHYTHMS

ABSTRACT Averaged visual evoked responses (AER) to sine wave light and to light flashes were recorded in seven subjects trained to control alpha rhythms. All seven subjects demonstrated a greater AER amplitude to sine wave light when there was high or abundant alpha in the EEG than when the alpha was low or almost entirely absent. Two of the early waves of the flash AER were usually greater in amplitude during periods of high alpha. A cycloplegic agent was shown to have no effect upon this finding, nor did varying the frequency of sine wave light stimulation. Period analysis of the EEG showed more activity at both low and high frequency bands during periods of low alpha. Auditory evoked response amplitudes were not significantly different between the high and low background alpha conditions. These results were discussed in relation to current views correlating AERs with attentive states.