Neuroelectric evidence of hypnotic hypoesthesia on the sensory and limbic processing of somatosensory signals

A large literature indicated hypnosis as a useful tool to reduce pain perception, especially in the high susceptible individuals. However, due to different methodological aspects, it was still not clear whether hypnosis modulates the early sensory processing of the stimuli or if it affects only the later stages of affective processing. In the present study, we measured the EEG activity of subjects whit a medium level of hypnotisability while receiving electrical non-painful stimuli on the median nerve in the conditions of awake and hypnosis with suggestions of hypoesthesia. Subjective reports indicated that hypnosis reduced both the sensory and the affective perception of the stimuli. ERP data revealed that hypnotic hypoesthesia reduced the activity of both the early (N20) and the late (P100, P150, P250) somatosensory evoked potentials (SEP). Neuroelectric source imaging further confirmed the top-down hypnotic modulation of a network of brain areas including the SI (N20), SII (P100), right anterior insula (P150), and cingulate cortex (P150/P250). Further, analysis on the preparatory slow waves revealed that hypnosis reduced the pre-stimulus activity over the prefrontal and parietal areas associated with the top-down control and the anticipatory attention, respectively.Present study provides neurophysiological evidence to the hypnotic regulation of somatosensory inputs outside of pain perception. Moreover, because present subjects were randomly selected regardless of their level of hypnotisability, present findings can be considered as representative of the general population.