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

Abstract

The relevance of formal hypnotic induction to the experience of trance and its neural correlates is not clear, in that hypnotizability, beliefs and expectation of hypnosis may play a major role. The aim of the study was assessing the EEG brain activity of participants with high (highs) or low hypnotizability scores (lows), aware of their hypnotizability level and informed that the session will include simple relaxation, formal hypnotic induction and neutral hypnosis. A total of 16 highs and 15 lows (according to the Stanford Hypnotic Susceptibility Scale, form A) were enrolled. Their EEGs were recorded during consecutive conditions of open/closed-eyes relaxation, hypnotic induction, neutral hypnosis and post hypnosis not interrupted by interviews. The studied variables were theta, alpha and gamma power spectral density (PSD), and the Determinism (DET) and Entropy (ENT) of the EEG signal Multidimensional Recurrence Plot (mRP). Highs reported significantly greater changes in their state of consciousness than lows across the session. The theta, alpha and gamma PSD did not exhibit condition-related changes in both groups. The Alpha PSD was larger in highs than in lows on midline sites, and the different sides/regions’ theta and gamma PSD were observed in the two groups independently from conditions. ENT showed no correlation with hypnotizability, while DET positively correlated with hypnotizability during hypnosis. In conclusion, the relevance of formal hypnotic induction to the experience of trance may be scarce in highs, as they are aware of their hypnotizability scores and expecting hypnosis. Cognitive processing varies throughout the session depending on the hypnotizability level.

Hypnosis measured with monitors of anesthetic depth – EEG changes during the test for Harvard Group Scale of Hypnotic Susceptibility

“…In the present study, the values of BIS and CSI during the various phases of HGSHS did not differ between high-and low-suggestible subjects (Figure 6). This is in line with a recent study that found that the power spectrum density of alpha, theta, and gamma bands does not support the relevance of the hypnotic induction to the highs' experience of hypnosis (Callara et al, 2023) and thus to hypnotic susceptibility scores. A definitive EEG-based signature for hypnosis and hypnotizability is not yet established (De Pascalis, 1999).…”

“…Only 36% of subjects classified as highly suggestible according to the HGSHS reached the same group affiliation in the SHSS:C (Kihlstrom, 2015). Furthermore, it might be of critical importance whether the test subject is aware of his or her suggestibility group before the BIS monitoring or not (Callara et al, 2023). This holds for many studies where participants are pre-selected for high suggestibility, as is common in hypnosis research.…”

“…Such conditions are the hypnotic state (after hypnotic induction) that renders "suggestibility" to "hypnotizability, " or a "natural trance" induced by acute medical situations (Cheek, 1962). The performance after suggestions, namely the experience of hypnotic phenomena with regard to muscular, sensory, and cognitive functions, is therefore not strictly dependent on a formal hypnotic induction and hypnotic depth (Callara et al, 2023). Only in approximately 50% of cases is suggestibility enhanced by hypnotic trance induction (Kirsch, 2000).…”

Neuroanthropology of shamanic trance: a case study with a ritual specialist from Mexico

“…Regarding the limpia , particularly during the initial preparation, alpha activity involving resting and relaxed but attentive states of wakefulness was observed ( Sanei and Chambers, 2007 ). Some authors have suggested that alpha activity is the first EEG element affected by preparation for a non-ordinary state of consciousness – for example, in hypnosis or in transcendental meditation that elicits a sensation of completeness in practitioners with several years of experience ( De Pascalis and Santarcangelo, 2020 ; Callara et al, 2023 ). This alpha state would suggest that practice and training configure a state of consciousness similar to the transition to stage 1 sleep, with certain similarly hypnagogic effects ( Lyubimov, 1999 ; Hankey, 2006 ).…”

“…Transcendental meditation is associated with brain activity that oscillates between alpha and beta waves ( Lyubimov, 1999 ). Hypnosis has been associated with theta and alpha frequencies, although gamma activity is particularly recurrent in people with high hypnotizability ( De Pascalis and Santarcangelo, 2020 ; Callara et al, 2023 ); in Tibetan Buddhist monks, an increase in gamma frequencies has been reported during compassion meditation ( Lutz et al, 2004 ). Other neuroimaging techniques have been used in some reports.…”