Hypnosis induces a changed composition of brain oscillations in EEG: a case study

Cognitive functions associated with the frontal lobes of the brain may be specifically involved in hypnosis. Thus, the frontal area of the brain has recently been of great interest when searching for neural changes associated with hypnosis. We tested the hypothesis that EEG during pure hypnosis would differ from the normal non-hypnotic EEG especially above the frontal area of the brain. The composition of brain oscillations was examined in a broad frequency band (1–30 Hz) in the electroencephalogram (EEG) of a single virtuoso subject. Data was collected in two independent data collection periods separated by one year. The ‘hypnotic’ and ‘non-hypnotic’ conditions were repeated multiple times during each data acquisition session. We found that pure hypnosis induced reorganization in the composition of brain oscillations especially in prefrontal and right occipital EEG channels. Additionally, hypnosis was characterized by consistent right-side-dominance asymmetry. In the prefrontal EEG channels the composition of brain oscillations included spectral patterns during hypnosis that were completely different from those observed during non-hypnosis. Furthermore, the EEG spectral patterns observed overall during the hypnotic condition did not return to the pre-hypnotic baseline EEG immediately when hypnosis was terminated. This suggests that for the brain, the return to a normal neurophysiological baseline condition after hypnosis is a time-consuming process. The present results suggest that pure hypnosis is characterized by an increase in alertness and heightened attention, reflected as cognitive and neuronal activation. Taken together, the present data provide support for the hypothesis that in a very highly hypnotizable person (a hypnotic virtuoso) hypnosis as such may be accompanied by a changed pattern of neural activity in the brain. Copyright © 2007 British Society of Experimental & Clinical Hypnosis. Published by John Wiley & Sons, Ltd.