Personal Space Regulation in Schizophrenia

Abstract

Representation and regulation of the space surrounding the body (i.e., the buffer zone between the self and others) play a central role in one’s adaptive interactions with the external world. There are at least two distinct ways to approach the study of the personal space. Peripersonal Space (PPS) refers to the multisensory interface surrounding the body within one’s grasp (reaching space) (Rizzolatti et al., 1997; Makin et al., 2009; Serino et al., 2011). Interpersonal distance (IPD) is characterized as a safety zone or the social comfort space that individuals prefer to maintain between themselves and others (Hall, 1966; Hayduk, 1978). The phenomenology of weakened self-boundary is a hallmark of schizophrenia but it has rarely been investigated in the context of disrupted PPS or IPD. Moreover, the role of social and emotional factors on the regulation of the personal space is poorly understood. To address this gap, novel experimental paradigms were implemented in immersive virtual reality environment to quantify PPS and IPD in individuals with schizophrenia (SZ) and control participants (CO). A multisensory integration task was used to estimate the PPS and a stop-distance task was used to measure IPD. To examine the potential impact of social and emotional factors, the stimuli were manipulated to convey appropriate contexts. In the first study, the effect of physical (Study 1A) and social threat (Study 1B) on PPS was examined. In Study 2, various avatars with descriptions, designed to prompt positive or negative emotion, were used to examine the malleability PPS (Study 2A) and IPD (Study 2B) and its associations to symptoms and social functioning in SZ. Furthermore, since adaptive regulation of personal space has been suggested as a potential treatment target (Sambo & Iannetti, 2013; Taffou & Viaud-Delmon, 2014; Kennedy & Adolphs, 2014), the clinical significance of personal space representation was investigated. In Study 3, PPS and IPD were utilized as outcome measures for a virtual reality (VR) based social skills training study. We found that personal space representation was altered under various social and emotional contexts in SZ compared with CO. In general, SZ showed a reduced flexibility in the regulation of personal space in response to socio-emotional changes in the environment. Personal space parameters, clinical symptoms and social functioning were closely associated, which highlights the significance of personal space regulation in schizophrenia. Importantly, we found that abnormal representation of personal space can be ameliorated through a simulation-based, social skills training program over a course of 8 sessions. Overall, these results indicate that mechanisms underlying self-disturbances in schizophrenia involve abnormalities of personal space regulation, and that these difficulties are associated with clinical symptoms and social dysfunctions. Future studies will need to further examine and analyze more specific parameters of PPS and IPD through continued innovations in methodology.