Hypnotic Susceptibility, Alpha Waves and 40-H2 EEG Rhythm, and Personality

Abstract

One of the main problems of EEG studies on hypnosis is the attempt to distinguish the brain activity of a postulated hypnotic state from that known to characterize the waking and sleeping states. One question is the relationship of basic subject differences, i.e., “trait” differences, to the level of hypnotic susceptibility. In the late 1960s, the enhancement of EEG recording technique with quantification of filtered EEG bandwidths allowed better evaluation of the EEG and hypnotic susceptibility relationship. Most of the correlational studies of EEG and hypnotizability have measured alpha rhythm. Two major research trends have influenced the search for EEG correlates of hypnosis and hypnotic susceptibility: (a) attempts to evaluate the correlation between baseline alpha levels and hypnotic susceptibility; and (b) attempts to delineate differences between high and low hypnotizables in functional asymmetry of the two cerebral hemispheres. The former trend derived from the presumption of operant control of alpha rhythm (Kamiya, 1969) and its concurrence with an altered state of consciousness (Anand, Chhina, & Singh, 1961; Kasamatsu & Hirai, 1969; Tart, 1969): if alpha production had been related to hypnotic susceptibility, then an increase of alpha production by means of voluntary control procedures could have produced an enhancement of hypnotizability in low susceptible subjects. The latter trend arose from the first studies devoted to understanding functional hemispheric asymmetry (Sperry, 1968; Gazzaniga, 1970; Kinsbourne & Smith, 1974; Kimura, 1973). Despite technological and methodological advances, both lines of research have produced some equivocal results.