Predisposition to Out-of-Body Experience (OBE) is associated with aberrations in multisensory integration:psychophysiological support from a “rubber-hand illusion” study

It has been argued that disorders in body-ownership and aberrant experiences in self-consciousness are due to biases in multisensory integration. Here we examine whether such biases are also associated with spontaneous Out-of-Body Experiences (OBEs) in a non-clinical population. One-hundred and eighty participants took part in a rubber-hand illusion (RHI) experiment with synchronous and asynchronous visual and tactile stimulation. A realistic threat was delivered to the rubber-hand after a fixed period of stimulation. Self-report exit questionnaires measured the subjective strength of the illusion and psychophysiological measures (skin conductance responses / finger temperature) provided an objective index of fear / anxiety towards the threat. Control participants reported a stronger RHI, and revealed larger threat-related skin conductance responses during synchronous compared with asynchronous brushing. For participants predisposed to OBEs, the magnitude of the skin conductance was not influenced by brushing synchrony - fear responses were just as strong in the asynchronous condition as they were in the synchronous condition. There were also no reliable effects of finger-temperature for either group. Collectively, these findings are taken as support for the presence of particular biases in multisensory integration (perhaps via predictive coding mechanisms) in which imprecise top-down tuning occurs resulting in aberrant experiences in self-consciousness even in non-clinical hallucinators

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

Introduction: Depersonalisation and derealisation disorders refer to feelings of detachment and dissociation from one’s “self” or surroundings. A reduced sense of self (or “presence”) and emotional “numbness” is thought to be mediated by aberrant emotional processing due to biases in self-referent multi-sensory integration. This emotional “numbing” is often accompanied by suppressed autonomic arousal to emotionally salient stimuli. Methods: 118 participants completed the Cambridge Depersonalisation scale [Sierra, & Berrios, 2000. The Cambridge Depersonalisation Scale: A new instrument for the measurement of depersonalisation. Psychiatry Research, 93, 153–164)] as an index of dissociative anomalous experience. Participants took part in a novel “Implied Body-Threat Illusion” task; a pantomimed injection procedure conducted directly onto their real body (hand). Objective psychophysiological data were recorded via standardised threat-related skin conductance responses and finger temperature measures. Results: Individuals predisposed to depersonalisation/derealisation revealed suppressed skin conductance responses towards the pantomimed body-threat. Although the task revealed a reliable reduction in finger temperature as a fear response, this reduction was not reliably associated with measures of dissociative experience. Conclusions: The present findings significantly extend previous research by revealing emotional suppression via a more direct body-threat task, even for sub-clinical groups. The findings are discussed within probabilistic and predictive coding frameworks of multi-sensory integration underlying a coherent sense of self

Fractionating the unitary notion of dissociation:disembodied but not embodied dissociative experiences are associated with exocentric perspective-taking

It has been argued that hallucinations which appear to involve shifts in egocentric perspective (e.g., the out-of-body experience, OBE) reflect specific biases in exocentric perspective-taking processes. Via a newly devised perspective-taking task, we examined whether such biases in perspective-taking were present in relation to specific dissociative anomalous body experiences (ABE) - namely the OBE. Participants also completed the Cambridge Depersonalization Scale (CDS; Sierra and Berrios, 2000) which provided measures of additional embodied ABE (unreality of self) and measures of derealization (unreality of surroundings). There were no reliable differences in the level of ABE, emotional numbing, and anomalies in sensory recall reported between the OBE and control group as measured by the corresponding CDS subscales. In contrast, the OBE group did provide significantly elevated measures of derealization ("alienation from surroundings" CDS subscale) relative to the control group. At the same time we also found that the OBE group was significantly more efficient at completing all aspects of the perspective-taking task relative to controls. Collectively, the current findings support fractionating the typically unitary notion of dissociation by proposing a distinction between embodied dissociative experiences and disembodied dissociative experiences - with only the latter being associated with exocentric perspective-taking mechanisms. Our findings - obtained with an ecologically valid task and a homogeneous OBE group - also call for a re-evaluation of the relationship between OBEs and perspective-taking in terms of facilitated disembodied experiences

The depersonalized brain:New evidence supporting a distinction between depersonalization and derealization from discrete patterns of autonomic suppression observed in a non-clinical sample

Depersonalization and Derealization are characterised by feelings of detachment from one’s bodily self/surroundings and a general emotional numbness. We explored predisposition to trait-based experiences of depersonalization/derealization-type experiences and autonomic arousal toward simulated body-threats, which were delivered to the participant’s own body (i.e. Self) and when observed being delivered to another individual (i.e. Other). Ninety participants took part in an “Implied Body-Threat Illusion” task (Dewe, Watson, & Braithwaite, 2016) and autonomic arousal was recorded via standardised skin conductance responses and finger temperature. Autonomic suppression in response to threats delivered to the Self correlated with increases in trait-based depersonalization-type experiences. In contrast, autonomic suppression for threats delivered to Others correlated with trait-based derealization-like experiences. Body-temperature and anticipatory arousal did not correlate reliably with predisposition to depersonalization- or derealization-type experiences. The theoretical implications of these findings are discussed in terms of a fronto-limbic autonomic suppression mechanism

The unreal self: A psychophysiological and psychological examination of dissociative body experiences in non-clinical samples

This thesis examines the neurocognitive biases of body-specific emotional processing in those predisposed to latent biases of depersonalization / derealization (DP/DR) experience. DP/DR is characterised by dissociative feelings of self-consciousness and dulled emotional experience. Emotional arousal was recorded via psychophysiological measures (skin conductance responses: SCRs, and body temperature) in relation to salient, body-related stimuli consisting of aversive simulated body-threats (e.g. injection procedures and fingernail removal). Body-threats were delivered either directly to the participant’s body, observed on a second individual present in the same room, or observed via dynamic movie clips. The principal findings across all empirical studies demonstrated significantly reduced emotional arousal (SCRs) to aversive body-threats in those predisposed to DP/DR experiences. That is, emotional suppression was observed for body-threats delivered to the “self” (participant’s own body), and when observed on “others” in the same room and via movie clips. Crucially, this suppression was specific to aversive body-threat stimuli, and was not observed for baseline (non-body-related) stimuli or measures of baseline / anticipatory arousal. Body-temperature was not mediated by DP/DR experience. Collectively, this work significantly extends previous research and theoretical accounts of DP/DR by utilising aversive body-related stimuli to demonstrate selective biases of emotion regulation in non-clinical instances of DP/DR. Warning: Please be advised, the content presented in this research thesis contains discussion and images of threatening and violent behaviours (simulated scenarios) toward a human body (i.e. blood / gore, knives and injection procedures) that some individuals may find unpleasant, offensive, or distressin

The Cortical Hyperexcitability Index (CHi) : a new measure for quantifying correlates of visually driven cortical hyperexcitability

Introduction: Aberrations of visual experience, including visual hallucinations and visual distortions are known to be associated with increased cortical hyperexcitability. As a consequence, the presence, intensity and frequency of certain experiences may well be indicative of an underlying increase in cortical hyperexcitability. Method: The current study presents a new proxy measure of cortical hyperexcitability, the Cortical Hyperexcitability Index (CHi). Two-hundred and fifty healthy participants completed the CHi with the results subjected to Exploratory Factor Analysis (EFA). Results: The EFA revealed a 3-factor model as the most parsimonious solution. The 3 factors were defined as; (i) heightened visual sensitivity and discomfort; (ii) negative aura-type visual aberrations; and, (iii) positive aura-type visual aberrations. The identification of 3-factors suggests that multiple mechanisms underlie the notion of cortical hyperexcitability, providing researchers with new and greater precision in delineating these underlying features. Conclusion: The factorial structure of the CHi, and the increased precision could aid the interpretation of findings from neuroscientific (i.e., brain-imaging / stimulation) examinations of cortical processes underlying aberrant perceptions across a host of clinical, neurological, and pathological conditions. As a consequence, the CHi is a useful and comprehensive proxy measure of cortical hyperexcitability with considerable scientific and clinical utility