Ketamine reduces the neural distinction between self- and other-produced affective touch - a double-blind placebo-controlled study

A coherent sense of self is crucial for social functioning and mental health. The N-methyl-D-aspartate antagonist ketamine induces short-term dissociative experiences, modelling an altered state of self-perception. This randomized double-blind placebo-controlled within-subject study investigated the mechanisms for ketamine’s effects on the bodily sense of self. Participants received intravenous ketamine while performing self-touch and receiving touch by someone else during functional MRI – a previously established neural measure of self-other-distinction. Ketamine administration elicited dissociation and reduced neural activity associated with self-other-distinction in the right temporoparietal cortex. The temporoparietal cortex showed higher connectivity to somatosensory cortex and insula during other- compared to self-touch. This difference was augmented by ketamine, and correlated with dissociation strength. We demonstrate that disrupting the self-experience through ketamine-administration affects neural activity associated with self-other-distinction in a region involved in touch perception and social cognition, providing further evidence for the intricate relationship of the bodily self with the tactile sense.