Own-body perception in body dysmorphic disorder.

2017-02-15T04:35:06Z (GMT) by Kaplan, Ryan Anthony
The aim of this thesis was to investigate own-body perception in body dysmorphic disorder(BDD). People with BDD perceive one or more aspects of their appearance to be aesthetically defective or grossly unattractive, even though their appearance is typically judged by others as normal. They become preoccupied with their supposed appearance defects and, as a result, often suffer immense psychological distress and functional impairment. People with BDD often present with significant comorbid mental illnesses, particularly depressive illnesses and anxiety disorders secondary to the BDD. Despite considerable research into BDD in recent years, few prior studies have investigated the perceptual aspect of BDD. The research program described here was concerned with understanding the distortions in own-body perception that people with BDD appear to be affected by. The focus of the thesis is the investigation of sensory processes that are central to own-body perception. Specifically, these are perceptual set-shifting, proprioception, and multisensory integration. Three studies are reported here. The first is an investigation of perceptual and cognitive set-shifting in which mean performance of a group of people with BDD (n = 17) on the Uznadze (haptic) illusion and the Brixton Test of Spatial Anticipation was expected to be significantly poorer than that of a healthy control (HC) group (n = 17) and a psychiatric control (SZ) group (n = 17) composed of people with schizophrenia spectrum disorders. A negative association between set-shifting ability and obsessive-compulsive BDD symptoms was also predicted. The second study is an investigation of proprioception and multisensory integration in the absence of vision which employed an angle adjustment task that participants completed blindfolded. Angle adjustment accuracy was predicted to be poorer among the BDD than control groups, and the BDD group was predicted to have slower task completion times than the other two groups. The third study employed the rubber hand illusion (RHI) to further investigate multisensory integration processes and the contribution of vision to multisensory processing in body perception. It was predicted that people with BDD would demonstrate enhanced susceptibility to the RHI relative to the control groups, and that there would be positive correlations between BDD-relevant symptoms and traits and RHI susceptibility. Across the three studies, no significant group differences in task performance or illusion experience were observed. In the set-shifting study, a positive correlation between BDD obsessive-compulsive symptoms and cognitive, but not perceptual, set-shifting ability was observed. In the RHI study, there were positive correlations between RHI susceptibility and body dissatisfaction variables. Thus, the notion that the distortions in own-body perception observed in BDD may be the result of problems in proprioceptive and multisensory aspects of bodily perception was not supported by the data. These results are discussed in the context of the existing BDD literature and relevant literature from related disorders. The possible role of aberrant visual processes in own-body perception distortions in BDD is discussed, and a speculative model of perceptual factors in BDD behaviours and cognitions is proposed.