Is Hypnotic Induction Necessary to Experience Hypnosis and Responsible for Changes in Brain Activity?

Area of Science:

• Neuroscience
• Psychology

Background:

• The role of formal hypnotic induction in trance experiences and their neural underpinnings remains unclear.
• Individual differences in hypnotizability, beliefs, and expectations significantly influence hypnotic states.

Purpose of the Study:

• To investigate the electroencephalogram (EEG) brain activity in individuals with high and low hypnotizability scores during various hypnotic conditions.
• To explore the relationship between hypnotizability and specific EEG measures, including power spectral density (PSD) and recurrence plot metrics.

Main Methods:

• EEG data were collected from 16 high and 15 low hypnotizability participants (Stanford Hypnotic Susceptibility Scale, form A).
• Participants underwent conditions including relaxation, formal hypnotic induction, and neutral hypnosis.
• EEG variables analyzed included theta, alpha, and gamma PSD, and Determinism (DET) and Entropy (ENT) from multidimensional recurrence plots (mRP).

Main Results:

• High hypnotizability individuals reported greater changes in consciousness compared to low hypnotizability individuals.
• Alpha PSD was higher in high hypnotizability individuals at midline sites; theta and gamma PSD differed between groups across conditions.
• Determinism (DET) positively correlated with hypnotizability during hypnosis, while Entropy (ENT) did not correlate.

Conclusions:

• Formal hypnotic induction may have limited relevance for trance experience in highly hypnotizable individuals aware of their scores and expecting hypnosis.
• Cognitive processing during hypnosis is dependent on an individual's level of hypnotizability.