Inhibition of retrieval in hypnotic amnesia: dissociation by upper-alpha gating

Brain Functional Correlates of Resting Hypnosis and Hypnotizability: A Review

This comprehensive review delves into the cognitive neuroscience of hypnosis and variations in hypnotizability by examining research employing functional magnetic resonance imaging (fMRI), positron emission tomography (PET), and electroencephalography (EEG) methods. Key focus areas include functional brain imaging correlations in hypnosis, EEG band oscillations as indicators of hypnotic states, alterations in EEG functional connectivity during hypnosis and wakefulness, drawing critical conclusions, and suggesting future research directions. The reviewed functional connectivity findings support the notion that disruptions in the available integration between different components of the executive control network during hypnosis may correspond to altered subjective appraisals of the agency during the hypnotic response, as per dissociated and cold control theories of hypnosis. A promising exploration avenue involves investigating how frontal lobes' neurochemical and aperiodic components of the EEG activity at waking-rest are linked to individual differences in hypnotizability. Future studies investigating the effects of hypnosis on brain function should prioritize examining distinctive activation patterns across various neural networks.

Eating Behavior-Choice or Reconstruction of Past Experience? A Randomized Clinical Trial of Changing Eating Intentions of Healthy Adults Through Hypnotic Suggestions

Recent meta-analyses have shown that psychological interventions have a small to medium effect on weight loss. We propose here a different approach to changing eating intentions. According to the Free Will literature, people decide to act before they acknowledge it, and they decide based on the reconstruction of previous experiences. The action can thus be inhibited immediately (max 100 ms) after awareness. We wanted to test if intervention based on this model, using hypnotic suggestions, can effectively change the intentions of eating. This study aims to identify which format of hypnotic suggestion can be more effective in changing eating intentions regarding high-calorie foods. Therefore, 88 healthy adult participants randomized in four groups received one session of hypnotic induction and suggestions or placebo. We measured the eating intentions through a computer task in which participants could choose pictures of low and high caloric food before, during, and after hypnosis. For the within-subject effect, results showed that two types of hypnotic suggestions significantly impacted the intentions of eating on high-calorie foods with large-effect, namely Cognitive Rehearsal (d = 0.81, p < .001) and Memory Substitution (d = 0.82, p < .001). After controlling for pretest ratings, we found a significant between-effect: the Cognitive Rehearsal group differed significantly from the Control in terms of intentions of eating (d = 0.85, p < .05). We conclude that hypnosis with Cognitive Rehearsal suggestions can help to positively impact the intentions of eating.

Higher hypnotic suggestibility is associated with the lower EEG signal variability in theta, alpha, and beta frequency bands

Variation of information in the firing rate of neural population, as reflected in different frequency bands of electroencephalographic (EEG) time series, provides direct evidence for change in neural responses of the brain to hypnotic suggestibility. However, realization of an effective biomarker for spiking behaviour of neural population proves to be an elusive subject matter with its impact evident in highly contrasting results in the literature. In this article, we took an information-theoretic stance on analysis of the EEG time series of the brain activity during hypnotic suggestions, thereby capturing the variability in pattern of brain neural activity in terms of its information content. For this purpose, we utilized differential entropy (DE, i.e., the average information content in a continuous time series) of theta, alpha, and beta frequency bands of fourteen-channel EEG time series recordings that pertain to the brain neural responses of twelve carefully selected high and low hypnotically suggestible individuals. Our results show that the higher hypnotic suggestibility is associated with a significantly lower variability in information content of theta, alpha, and beta frequencies. Moreover, they indicate that such a lower variability is accompanied by a significantly higher functional connectivity (FC, a measure of spatiotemporal synchronization) in the parietal and the parieto-occipital regions in the case of theta and alpha frequency bands and a non-significantly lower FC in the central region's beta frequency band. Our results contribute to the field in two ways. First, they identify the applicability of DE as a unifying measure to reproduce the similar observations that are separately reported through adaptation of different hypnotic biomarkers in the literature. Second, they extend these previous findings that were based on neutral hypnosis (i.e., a hypnotic procedure that involves no specific suggestions other than those for becoming hypnotized) to the case of hypnotic suggestions, thereby identifying their presence as a potential signature of hypnotic experience.