Gamma-band (30-40 Hz) connectivity during hypnosis in individuals with equal high hypnotizability but different dissociative experiences: a preliminary study

Abstract

Background Most electrophysiological studies in hypnosis have divided individuals into two groups with high and low hypnotizability. However, this classification has been subjected to considerable criticism. The most important of these criticisms is that highly hypnotizable individuals can be divided into different groups due to their heterogeneity. Methods We selected 20 people with a score of eight or higher on the Stanford Hypnotic Susceptibility Scale C (SHSSC). We recorded the 19-channel EEG activity of the subjects in pre-hypnosis (baseline) and hypnosis conditions. We performed Dissociative Experiences Scales (DES) on them. We divided the subjects based on their DES score into two groups as high dissociative (HD) and low dissociative (LD). We predict that the two groups will have different gamma-band (30–40 Hz) connectivity despite equal hypnotizability. Results We found that both highly hypnotizable groups had reduced gamma connectivity during hypnosis. However, the characteristic gamma connectivity changes in the LD group decreased in the interhemispheric medial frontal cortex (MPFC). Furthermore, the HD group showed reduced gamma connectivity in the left frontotemporal network. Conclusions Indeed, the LD group showed reduced gamma in the "default mode network" and the HD group in the "executive control network".