EEG concomitants of hypnosis and hypnotic susceptibility.

Electroencephalograph (EEG) measures described high- and low-hypnotizable participants in terms of 3 conditions: an initial baseline period; baselines preceding and following a standard hypnotic induction; and during the induction. The following results were obtained. 1. High and low-hypnotic susceptible participants displayed a differential pattern of EEG activity during the baseline period, characterized by greater theta power in the more frontal areas of the cortex for the high-susceptible participants. 2. In the period preceding and following a standardized hypnotic induction, low-susceptible participant displayed an increase in theta activity, whereas high-susceptible participants displayed a decrease. 3. During the actual hypnotic induction itself, theta power significantly increased for both groups in the more posterior areas of the cortex, whereas alpha activity increased across all sites. Implications of these data include the possibility of psychophysiological measures offering a stable marker for hypnotizability, and anterior/posterior cortical differences being more important than hemispheric foci for understanding hypnotic processes.