Browsing by Subject "hypnosis"

Objective: To contribute to the theory-building on hypnosis by studying the possible changes that hypnosis causes in the electroencephalographic (EEG) spectral power in highly hypnotisable individuals. In accordance with previous literature, hypnosis was hypothesised to cause an increase in theta (4–8 Hz) power and a change in gamma (25–45 Hz) power. Methods: Nine highly hypnotisable individuals (8 females) participated. Continuous EEG was recorded at ten electrodes during four conditions: prehypnosis, neutral hypnosis, hypnotic suggestion, and posthypnosis. During all conditions, the participants watched a monotonous video while sinusoidal tones following an oddball paradigm played silently in the background. The participants were instructed not to pay any attention to the tones, and in the suggestion-condition a suggestion to hear all tones as similar in pitch was given. Nine repeated-measures analyses of variance, one for each frequency range, were performed. For research questions 2 and 3, the participants were divided into two groups depending on their responsiveness to a hallucinatory suggestion in the screening phase, and the analyses were then run again. Results: No differences between conditions were found in the theta range, but a decrease was found in the gamma range during hypnosis compared with wakefulness (posthypnosis). Spectral power differences depending on responsiveness to the hallucinatory suggestion were also found. Conclusions: The findings support the hypothesis of changed gamma-frequency power during hypnosis, but not the theory of increased theta frequencies as a marker of hypnosis. A tentative theoretical connection between reduced peripheral awareness and reduced gamma power in hypnosis is presented.