Neuroelectric evidences of top-down hypnotic modulation associated with somatosensory processing of sensory and limbic regions.

A large literature indicated hypnosis as a useful tool to reduce pain perception, especially in 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 with a medium level of hypnotizability 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 hypnosis reduced the activity of both the early (N20) and the late (P100, P150, P250) SEP components. 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). The present study provides neurophysiological evidence to the hypnotic regulation of somatosensory inputs outside of pain, that is since the earliest stage of thalamocortical processing. Also, because present subjects were selected regardless of the level of hypnotizability, inferences from the present study are more generalizable than investigations restricted to high-hypnotizable individuals.