Electroencephalography Oscillations During Prehypnosis and Hypnosis in Subjects With High and Low Dissociative Experiences.

Introduction: Hypnosis is a multifaceted phenomenon that refers to suggestions for creating desirable behavior, experience, and physiological changes. Most electroencephalographic (EEG) research in hypnosis has allocated people into two groups of high and low hypnotizables. Hence, the empirical data are somewhat controversial, and there is no general agreement about the neurophysiology of hypnosis. On the other hand, the dissociation theory of hypnosis posits that people candidates for hypnosis are typically prone to dissociation, and individuals divide into two groups: High dissociative (HD) and low dissociative (LD). If this assumption is true, such a state should be visible as a distinct pattern of changes in absolute power and functional connectivity between brain districts after a hypnotic induction in high but not in LD suggestible.

Methods: The final sample consisted of 20 participants who scored 6 or higher on the Stanford hypnotic susceptibility scale form C (SHSS: C). Then, we completed dissociative experiences scales (DES) on them. To assess the brain's electrical activity during hypnosis, a 19-channel EEG was recorded from 10 HD and 10 LD participants with their eyes closed before (baseline) and after the induction of hypnosis. We used EEG to measure absolute power and functional connectivity using coherence. We expected the two groups to have dissimilar EEG signal patterns despite equivalent hypnotizability.

Results: We found that in the delta, theta, alpha, beta, and gamma bands, both groups were different from the baseline to hypnosis. In addition, both groups showed different connectivity in hypnosis in four bands (delta, theta, alpha, and beta).

Conclusion: These findings indicate that although the LD and HD groups had equal hypnotizability, the episodic prospection tasks did not involve the same neural networks in the two groups.