Changes of the Event-Related Potentials during Hypnosis

Background: In psychology, hypnosis is classified into three stages: movement control stage (stage 1), sensory control stage (stage 2), and memory control stage (stage 3). However, this has not been verified scientifically. Therefore, we studied the cognitive ability, event-related potentials (ERPs), during different stages of hypnosis. Methods: There were two female subjects. One was of high hypnotizability and the other of low hypnotizability. ERP was elicited by a two-tone auditory discrimination task, recorded with 28 electrodes. The Global Field Power (GFP) and the Current Source Density (CSD) of the N100 and P300 components were calculated from the acquired brain waves. Results: Compared to prehypnosis, the amplitudes of N100 and P300 of the highly susceptible subject increased, but there was no difference among the three stages in hypnosis. For the lowly susceptible subject during hypnosis, the stages 2 and 3. For the subject with low hypnotizability, we thought that in stage 2 the frontal source had attenuated. Conclusion: The hypnotic state in a highly hypnotizability subject may be related to a near condition of relaxation, and the hypnotic state in a low hypnotizability subject may be related to a near condition of a tense state. The selective attention and cognitive ability increased during hypnosis in the highly hypnotizability subject, but decreased in the low hypnotizability subject. In addition, the disappeared subcomponent of 1 or 6 of N100 components in the low hypnotizability subject may be related to attention shift.