Imagined and Actual Movements with and without Suggestions for anesthesia in Subjects with Different Hypnotizability

Background: Hypnotizability is a psychophysiological trait associated with several differences including the level of functional equivalence (FE) between imagery and perception, i.e., the similarity of the cortical activations and network configurations associated with each of them. FE is stronger in high hypnotizability individuals (highs) than low hypnotizable participants (lows). In this framework, this study investigates the correlation between electroencephalogram (EEG) of imagined arm/hand movements (MI) and of actual movements performed in the absence of suggestions (M) and in the presence of suggestions of arm/hand anesthesia (MA) in highs and lows. Methods: The EEG alpha (8–12 Hz) and beta (13–25 Hz) absolute power, classically associated with movement preparation and execution, were studied in 18 highs and 17 lows classified according to the Stanford Hypnotic Susceptibility Scale, form A. EEG was recorded during M, MI, and MA. The subjective reports of imagery and the duration of movements were also studied. Results: The duration of movements did not differ between highs and lows. Highs reported better imagery during MI, greater perceived influence of the suggestion of anesthesia during MA, and lower cognitive efforts than lows for both tasks. In line with earlier studies, the spectral analysis did not reveal significant restructuring of the cortical activity during tasks in highs, whereas lows showed cortical changes during MI and MA indicating that they were able to mentally simulate movements and to accept suggestions for anesthesia during voluntary movement, despite their low hypnotizability scores. Conclusions: The present study indicates that unusual psychophysiological characteristics can differ in the response of individuals to suggestions.