Pain perception, somatosensory event-related potentials and skin conductance responses to painful stimuli in high, mid, and low hypnotizable subjects: effects of differential pain reduction strategies

In this study, pain perception, somatosensory event-related potential (SERP ) and skin conductance response (SCR) changes during hypnotic suggestions o f Deep Relaxation, Dissociated Imagery, Focused Analgesia, and Placebo, com pared with a Waking baseline condition, were investigated. SERPs were recor ded from frontal, temporal, central, and parietal scalp sites. Ten high, 9 mid, and 10 low hypnotizable right-handed women participated in the experim ent. The following measures were obtained: (1) pain and distress tolerance ratings; (2) sensory and pain thresholds to biphasic electrical stimulation delivered to the right wrist; (3) reaction time and number of omitted resp onses; (4) N2 (280 +/- 11 ms) and P3 (405 +/- 19 ms) peak amplitudes of SER Ps to target stimuli delivered using an odd-ball paradigm; (5) number of ev oked SCRs and SCR amplitudes as a function of stimulus repetition. Results showed, high, mid and low hypnotizables exhibited significant reductions of reported pain and distress ratings during conditions of Deep Relaxation/Su ggestion of Analgesia, Dissociated Imagery and Focused Analgesia. High hypn otizable subjects displayed significant reductions in pain and distress lev els compared to mid and low hypnotizables during Dissociated Imagery, Focus ed Analgesia and, to a lesser degree, during Deep Relaxation. Placebo condi tion did not display significant differences among hypnotizability groups. High hypnotizables, compared to mid and low hypnotizables, also showed sign ificant increases in sensory and pain thresholds during Dissociated Imagery and Focused Analgesia. High, mid, and low groups showed significant reduct ions in P3 peak amplitudes across all hypnosis conditions and, to a lesser degree, during Placebo. The temporal cortical region was the most sensitive in differentiating SERF responses among hypnotizability groups. On this re cording area the subjects highly susceptible to hypnosis displayed signific antly smaller P3 and greater N2 peaks during Focused Analgesia than did the other hypnotizable groups. In this condition highly susceptible subjects a lso reported the highest number of omitted responses and the shortest React ion Times. These subjects also showed faster habituation of SCRs when compa red with mid and low hypnotizables. During Dissociated Imagery and Focused Analgesia, highly hypnotizable subjects also disclosed a smaller total numb er of evoked SCRs than did mid and low hypnotizable subjects. The results a re discussed considering possible common and different mechanisms to accoun t for the effects of different hypnotic suggestions. (C) 1999 International Association for the Study of Pain. Published by Elsevier Science B.V.