Pain response in depersonalization:: A functional Imaging study using hypnosis in healthy subjects

Background: Depersonalization (DP) is characterized by persistent or recurrent episodes of detachment from one's self with reduced pain perception being a common feature. Alterations in the body schema similar to the cortico-limbic disconnection syndrome of pain asymbolia are suggested to be responsible for DP. In this study we used hypnosis to induce DP in healthy subjects and to examine neural patterns of pain perception in the state of DP by means of functional magnetic resonance imaging (fMRI). Methods: Pain perception was investigated in 7 healthy subjects with high susceptibility to hypnosis in three different mental states: waking state (N-W), hypnotic relaxation (H-R) and hypnotic DP (H-DP). Pain was induced with electrical stimulation to the median nerve at the right wrist. fMRI measurements were performed during all states. Results: Nociceptive stimuli led to an activation of the well described pain network including somatosensory and insular regions and the cerebellum. Activation was markedly reduced in the contralateral somatosensory cortex, parietal cortex ( Brodmann area 40, BA40), prefrontal cortex (BA9), putamen and the ipsilateral amygdala during H-DP. Subjects also reported a significant decrease in pain intensity from N-W to H-DP. Conclusion: Pain response during H-DP was reduced in sensory and affective pain-related areas, reflecting the diminished intensity of the perceived pain. Moreover, a network of cortical and subcortical areas that have been implicated in the perception of the own body was less responsive during DP, which might point to a specific neural mechanism underlying the `out-of-body' experience. Although the small number of subjects does not allow a generalization of our findings, H-DP seems to be a promising tool for the investigation of psychological and biological mechanisms of self-inflicted injuries as well as the mind-body interplay within the realm of psychosomatic disorders.