Differentiation of hypnosis and relaxation by analysis of narrow band theta and alpha frequencies

Narrow band theta and alpha activity were recorded over anterior and poster ior sites before, during, and after hypnosis in high and low hypnotically s usceptible subjects (N = 16). In theta, high susceptibles had greater activ ity posthypnosis, otherwise there were no group differences. These findings common to low and high susceptibles suggest that theta is an index of rela xation that continues after hypnosis in highs. In alpha in high susceptible s, posterior power increased from the prehypnosis to hypnosis conditions an d decreased posthypnosis. Exactly the converse effects were seen in lows. F urthermore, highs had greater alpha power than lows during both prehypnosis and hypnosis conditions, demonstrating an association of alpha with hypnot ic susceptibility. The results indicate that, whereas theta indexes relaxat ion, alpha indexes the hypnotic experience and susceptibility.