Modulating spinal activity with hypnosis: can hypnotic hypoesthesia modulate early somatosensory evoked potentials?

Introduction and aims: Effective pain management often requires approaches beyond pharmacological treatments and interest has been growing for the use of analgesic techniques such as hypnosis in the clinical field. Despite its increasing use, the mechanisms underlying hypnosis remain unclear. Previous studies have shown that hypnosis can reduce the RIII component of nociceptive withdrawal reflexes, suggesting involvement of descending modulatory pathways. This study aims to further investigate spinal mechanisms of hypnosis by examining the N13 components of somatosensory evoked potentials (SERPs) and exploring its effects on cortical SERPs. Methods: In this study, N13 and early cortical SERPs were recorded from healthy volunteers in response to median nerve stimulation under a normal waking and a hypnosis condition. Participants rated stimulus intensity and unpleasantness, and their hypnotizability was assessed using the Elkins Hypnotic Susceptibility Scale. Results: A decrease in the unpleasantness ratings, which was accompanied by a decrease in N20 and an increase in P40 amplitudes have been observed in the hypnosis condition as compared to the awake condition. No significant results have been found concerning N13 amplitudes. Conclusions: This study could not highlight any spinal modulation of hypnosis but found a modulation in the early cortical potentials. This could suggest that hypnosis can modulate somatosensory information since the first cortical processing.