Shared multisensory experience affects Others' boundary: The enfacement illusion in schizophrenia

Abstract

Schizophrenia has been described as a psychiatric condition characterized by deficits in one's own and others' face recognition, as well as by a disturbed sense of body-ownership. To date, no study has integrated these two lines of research with the aim of investigating Enfacement Illusion (EI) proneness in schizophrenia. To accomplish this goal, the classic EI protocol was adapted to test the potential plasticity of both Self-Other and Other-Other boundaries. Results showed that EI induced the expected malleability of Self-Other boundary among both controls and patients. Interestingly, for the first time, the present study demonstrates that also the Other-Other boundary was influenced by EI. Furthermore, comparing the two groups, the malleability of the Other-Other boundary showed an opposite modulation. These results suggest that, instead of greater Self-Other boundary plasticity, a qualitative difference can be detected between schizophrenia patients and controls in the malleability of the Other-Other boundary. The present study points out a totally new aspect about body-illusions and schizophrenia disorder, demonstrating that EI is not only confined to self-sphere but it also affects the way we discriminate others, representing a potential crucial aspect in the social domain.

Body illusions for mental health: a systematic review

“…Thirty-four studies used BIs to improve body representation in clinical populations. Eight studies used BIs toward a body part in patients with schizophrenia (Ferri et al, 2014;Ferroni et al, 2019;Lev-Ari et al, 2015;Peled et al, 2003;Prikken et al, 2019;Sandsten et al, 2020;K.N. Thakkar et al, 2011;Van Haren et al, 2018).…”

“…Two studies used the enfacement illusion (EI) (Ferroni et al, 2019;Sandsten et al, 2020). In the study conducted by Sandsten and colleagues (2020), healthy subject and patients with schizophrenia were exposed to a video showing a movie of the face of an "other" individual looking straight into the camera while receiving synchronous VTS on the face, or were alternative exposed to a movie of their self-face without tactile stimulus; results showed deviations in specular self-recognition in patients with schizophrenia compared to healthy controls.…”

“…In this systematic review, we presented a comprehensive overview of works in which BIs have been used to restore altered body representation in patients with psychiatric disorders such as schizophrenia, in which it has been found a perturbed sense of body ownership, and a weak sense of self (Ferri et al, 2014;Lev-Ari et al, 2015;Peled et al, 2003;Prikken et al, 2019;K.N. Thakkar et al, 2011;Van Haren et al, 2018), as well as an altered self-recognition (Sandsten et al, 2020), and the way in patients with schizophrenia discriminate others (Ferroni et al, 2019). Moreover, BIs have been also used in patients with eating disorders (Carey and Preston, 2019;Eshkevari et al, 2012Eshkevari et al, , 2014Keizer et al, 2014;Tagini et al, 2020;Zopf et al, 2016;Forghieri et al, 2016;Keizer et al, 2016), in which inner body perception is often disturbed presenting distortions or mismatches in discriminating how the body is perceived and how physically it is (Malighetti et al, 2020).…”

Altered Auditory Self-recognition in People with Schizophrenia

“…Overall, these results confirm that auditory self-recognition was altered in people with SZ. Disturbances in the processing of visual selfrecognition are well studied in people with SZ (Ferroni et al, 2019;Sandsten et al, 2019;She et al, 2017), whereas relatively few studies have focused on the processing of self in other domains, such as auditory. On the one side, it was well-known that hearing one's own voice recording from an outside source may sound dissimilar than hearing one's voice internally (i.e., there is distortion that occurs from bone conduction when perceiving one's own voice as it is produced during normal speech) ( Hughes & Nicholson, 2010).…”

“…Numerous neurophysiological studies have also found abnormalities in anatomical structures and functional activities related to face-processing (Lee et al, 2002;She et al, 2017). Interestingly, the multisensory paradigm of the enfacement illusion (EI) was introduced by Tsakiris (2008) to show how multisensory clues could affect self-face recognition (Ferroni et al, 2019;Sandsten et al, 2019). EI is a subjective experience of perceiving other's face as self-face under synchronous interpersonal multisensory stimulation.…”