Psychophysiological correlates of voluntary alpha control

To test the hypothesis that voluntary alpha control is at least partly mediated through self-induced changes in cortical activation level and bodily arousal, changes in several physiological indicants of such activity were systematically examined while subjects voluntarily produced and suppressed alpha activity. Physiological indicants consisted of cortical evoked potentials, eye motor activity, neck EMG, and skin conductance. Three male and three female subjects were pretrained to a specified criterion to produce and suppress alpha activity, using auditory feedback. Following pretraining, each subject participated in four experimental sessions under instructions to either produce or suppress alpha while keeping his eyes closed. Each session consisted of eight alternating three-minute trials of high and low alpha conditions with rest intervals between trials. During each session EEG activity was recorded monopolarly from the occiput with the reference electrode on the right earlobe. Filtered, integrated EEG consisting of alpha activity only, drove a frequency- modulated power driver connected to a speaker which provided continuous feedback in terms of the pitch of a tone. Cortical evoked potentials based on the presentation of 100 irregularly presented light flashes per trial were recorded with a Computer of Average Transients. Using the appropriate Grass Model 7 preamplifiers, skin conductance was recorded from the first and third fingers of the left hand; EMG from the trapezius neck muscle, and eye motor activity with electrodes placed diagonally across the eyes