Bodily Self-Dysfunction in Psychosis: Altered Neural and Spinal Response to Self-produced Sensations

Psychosis is often characterized by disturbances in the sense of self, with patients frequently misattributing self-produced sensations to external sources. While somatic hallucinations and misperceptions are common, the underlying disruptions in basic bodily self-processing remain unclear. We aimed to investigate alterations in bodily self-processing, including touch and interoception, in psychosis using a multimodal, multi-method approach. A total of 70 participants were included (35 patients diagnosed with psychotic disorders [DSM-IV F20-29], 35 age-and sex-matched controls). Participants performed self-/other-touch-tasks and interoceptive assessments during functional magnetic resonance imaging (fMRI), evoked potentials (EP) measurements, and/or behavioral and psychophysical tests. Primary outcomes included neural and behavioral responses to self-and externally-generated sensations (touch and heartbeat). Brain activation (fMRI), spinal responses (EPs), heartbeat perception and processing (EPs), and behavioral measures were analyzed, with preregistered hypotheses. Patients demonstrated heightened neural activity during touch tasks, including increased right superior temporal gyrus activation during self-touch and heightened activity in a right temporoparietal cluster during social touch. Tactile self-other distinction impairments were evident at the spinal cord level (EPs). Behaviorally, patients showed reduced differentiation in tactile thresholds for self-vs. other-touch. Interoceptive impairments included diminished cortical responses to heartbeat signals (EPs), lower interoceptive accuracy (heartbeat detection), and reduced self-reported interoceptive sensitivity. These findings reveal pervasive sensory and self-related disturbances in psychotic disorders. Impairments in differentiating self-and externally-evoked responses, detectable as early as the spinal cord level, may contribute to higher-order symptoms of psychosis.