The 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. Movement 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. Hypnotic 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. Hyperactivation 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.

Cortex. 2012 Jun 20. [Epub ahead of print] Burgmer M, Kugel H, Pfleiderer B, Ewert A, Lenzen T, Pioch R, Pyka M, Sommer J, Arolt V, Heuft G, Konrad C. Department of Psychosomatics and Psychotherapy, University Hospital Münster, Münster, Germany.