Subjects’ hypnotizability level affects somatosensory evoked potentials to non-painful and painful stimuli

Abstract

ObjectiveWe evaluated the working hypothesis that the EEG activity associated to non-painful and painful stimuli in condition of waking state (no hypnotic procedure) was related to the hypnotizability level. MethodsHypnotizability level was measured in 16 healthy subjects through the Italian version of the Stanford Hypnotic Susceptibility Scale (SHSS, score: 0–12). EEG data (56 electrodes) were recorded during non-painful and painful electrical stimuli applied to the left index finger. Cortical activity (vertex N1–P2 complex) was compared in subjects with low hypnotizability level (N=8, SHSS:0–6) vs. subjects with high hypnotizability level (N=8, SHSS:7–12). ResultsThe amplitude of the N1–P2 complex was lower in the High-hypnotizability compared to the Low-hypnotizability group over primary sensorimotor cortex (C3 and C4 electrodes) and centro-parietal midline areas (Cz and Pz electrodes) for non-painful and painful stimuli. The SHSS showed a statistically significant negative correlation with the vertex N1–P2 complex at C3 and Cz (r=−0.5, p<0.05) electrodes for non-painful stimuli. ConclusionCompared to the Low-hypnotizability subjects, High-hypnotizability subjects showed a reduced cortical activity related to non-painful and painful stimuli. SignificanceThe results suggest a relationship between hypnotizability and cortical activity related to non-painful and painful stimuli in the condition of waking state (no hypnotic effect).