Disturbances in Body Ownership in Schizophrenia: Evidence from the Rubber Hand Illusion and Case Study of a Spontaneous Out-of-Body Experience

Abstract

BackgroundA weakened sense of self may contribute to psychotic experiences. Body ownership, one component of self-awareness, can be studied with the rubber hand illusion (RHI). Watching a rubber hand being stroked while one's unseen hand is stroked synchronously can lead to a sense of ownership over the rubber hand, a shift in perceived position of the real hand, and a limb-specific drop in stimulated hand temperature. We aimed to assess the RHI in schizophrenia using quantifiable measures: proprioceptive drift and stimulation-dependent changes in hand temperature.MethodsThe RHI was elicited in 24 schizophrenia patients and 21 matched controls by placing their unseen hand adjacent to a visible rubber hand and brushing real and rubber hands synchronously or asynchronously. Perceived finger location was measured before and after stimulation. Hand temperature was taken before and during stimulation. Subjective strength of the illusion was assessed by a questionnaire.ResultsAcross groups, the RHI was stronger during synchronous stimulation, indicated by self-report and proprioceptive drift. Patients reported a stronger RHI than controls. Self-reported strength of RHI was associated with schizotypy in controls Proprioceptive drift was larger in patients, but only following synchronous stimulation. Further, we observed stimulation-dependent changes in skin temperature. During right hand stimulation, temperature dropped in the stimulated hand and rose in the unstimulated hand. Interestingly, induction of RHI led to an out-of-body experience in one patient, linking body disownership and psychotic experiences.ConclusionsThe RHI is quantitatively and qualitatively stronger in schizophrenia. These findings suggest that patients have a more flexible body representation and weakened sense of self, and potentially indicate abnormalities in temporo-parietal networks implicated in body ownership. Further, results suggest that these body ownership disturbances might be at the heart of a subset of the pathognomonic delusions of passivity.

Uncomfortably numb: new evidence for suppressed emotional reactivity in response to body-threats in those predisposed to sub-clinical dissociative experiences

“…In addition, previous research has argued that drops in body / finger temperature can reflect a psychophysiological anxiety response (Vinkers, et al, 2013), and this has been shown for non-clinical samples in relation to body illusions (full body illusions: Salomon et al, 2013; the RHI: Moseley et al, 2008;Kammers et al, 2011;Thakkar et al, 2011: though see also Hohwy & Paton, 2010;Paton et al, 2012 for failures to replicate). Therefore, finger temperature was measured as an additional objective index of threat-related anxiety, via a separate channel on the same MP36R unit described above.…”

“…Research has argued that the hypothalamus and preoptic area (PO) play crucial roles in effective body temperature regulation, and a wealth of research has explored thermoregulation with respect to behaviour such as psychological reactivity to stress (Hammel, 1968;Nagashima, Nakai, Tanaka, & Kanosue, 2000;Oka, 2015;Oka, Oka & Hori, 2001). Indeed, drops in finger temperature have been associated with fear / anxiety responses (Vinkers et al, 2013), and have been demonstrated under body-illusion conditions (full body illusions: Salomon, Lim, Pfeiffer, Gassert & Blanke, 2013; the Rubber-hand illusion, RHI: Moseley et al, 2008;Kammers, Rose, & Haggard, 2011;Thakkar, Nichols, McIntosh, & Park, 2011: though see also Hohwy & Paton, 2010;Paton, Hohwy, & Enticott, 2012 for failures to replicate). This has led some researchers to suggest that such drops in temperature could also be used as a reliable index of fear processing, and that temperature regulation must therefore involve higher, top-down cognitive processing between physiological regulation of the physical self and the conscious 'self' (Moseley et al, 2008).…”

Initial validation of a virtual blood draw exposure paradigm for fear of blood and needles

“…For example, the "rubber arm illusion", first introduced by Botvinick and Cohen in 1998 [3], pairs Virtual Blood Draw 4 tactile stimuli to one's actual arm with that observed on a rubber arm to induce a sense of "ownership" of the rubber arm. Drawing on recent research regarding optimal arm illusion parameters [3,5,20,34,36], the present study examined an extension of this approach by testing simulated ownership of a human arm depicted in virtual/digital format to facilitate exposure to a simulated blood draw. The blood draw procedure was selected due to its relevance to both blood and needles stimuli as well as syncopal response.…”

The ‘not-so-strange’ body in the mirror: A principal components analysis of direct and mirror self-observation

“…Schizophrenic patients are found to have stronger experiences of the strange face illusion compared to healthy controls (Caputo et al, 2012). Individuals suffering from schizophrenia are also found to have deficits in self recognition (Irani et al, 2006;Platek & Gallup, 2002) and body/action awareness (Louzolo et al, 2015;Thakkar et al, 2011), but these unusual experiences are also not confined to mirror viewing, such that, similar to dysmorphic traits, delusions and schizophrenic/delusion symptoms may be related to usual experiences, but not specifically when looking in a mirror.…”

“…Indeed, schizophrenia as well as schizotypal traits are thought to be related to deficits in self-face recognition (Irani et al, 2006;Platek & Gallup, 2002) and body/action perception (Louzolo, Kalckert, & Petrovic, 2015;Thakkar, Nichols, McIntosh, & Park, 2011), which seems compatible with the experiences of strange face illusions. For many conditions in which self and body perception is impaired these experiences focus predominantly on the body rather than the face, yet, to date, whether perceptual illusions can occur when viewing our body rather than our face in the mirror has not been investigated.…”