The mirror neuron system under hypnosis – Brain substrates of voluntary and involuntary motor activation in hypnotic paralysis

IntroductionThe neurobiological basis of non-organic movement impairments is still unknown. As conversion disorder and hypnotic states share many characteristics, we applied an experimental design established in conversion disorder to investigate hypnotic paralysis.MethodsMovement imitation and observation were investigated by functional magnetic resonance imaging (fMRI) in 19 healthy subjects with and without hypnotically induced paralysis of their left hand. Paralysis-specific activation changes were explored in a multivariate model and functional interdependencies of brain regions by connectivity analysis.ResultsHypnotic paralysis during movement imitation induced hypoactivation of the contralateral sensorimotor cortex (SMC) and ipsilateral cerebellum and increased activation of anterior cingulate cortex (ACC), frontal gyrus and insula. No paralysis-specific effects were revealed during movement observation.ConclusionsHyperactivation of ACC, middle frontal gyrus (MFG), and insula might reflect attention (MFG), conflict-detection (ACC) and self-representation processes (insula) during hypnotic paralysis. The lack of effects in movement observation suggests that early motor processes are not disturbed due to the transient nature of the hypnotic impairment.