Self-other boundary under social threat in schizophrenia

Spatial representation of the self plays a vital role constructing our sense of bodily self-boundary that distinguishes the self from others. This perceptual border, known as the peripersonal space (PPS), has been suggested to be altered in individuals with schizophrenia (SZ). PPS represents a protective defensive zone that triggers alarm signals upon threat detection; thus disrupted PPS could lead to social interactional difficulties. However, very little is known about the impact of threat on PPS. To address this gap, a visual-tactile response-time (RT) experiment was conducted in immersive virtual reality (VR) for SZ and matched controls (CO). Participants were asked to detect a tactile vibration on their hand while an avatar (either threatening or neutral) approached them. Avatars were presented at different distance from the participants. PPS size and slope were estimated by identifying significant RT drop at the hypothesized self-other boundary. We also examined the relationship between PPS parameters, clinical symptoms and social disconnection. There was no overall group difference in PPS size. Perceived social threat posed in the avatars sharpened the self-boundary in CO but not in SZ. In SZ, shallower PPS slope was associated with delusion, persecution, negative symptoms and loneliness but not in CO. These results show that the regulation of self-other boundary in response to impending social threat may be maladaptive in SZ. Further research is needed on the causal mechanisms between self-disturbance and social impairments.