Self motion perception involves the integration of visual, vestibular, somatosensory and motor signals. This article reviews the findings from single unit electrophysiology, functional and structural magnetic resonance imaging and psychophysics to present an update on how the human and non-human primate brain integrates multisensory information to estimate one’s position and motion in space. The results indicate that there is a network of regions in the non-human primate and human brain that processes self motion cues from the different sense modalities.
Self-face recognition, a hallmark of self-awareness, depends on 'off-line' stored information about one's face and 'on-line' multisensory-motor face-related cues. The brain mechanisms of how on-line sensory-motor processes affect off-line neural self-face representations are unknown. This study used 3D virtual reality to create a 'virtual mirror' in which participants saw an avatar's face moving synchronously with their own face movements. Electroencephalographic (EEG) analysis during virtual mirror exposure revealed mu oscillations in sensory-motor cortex signalling on-line congruency between the avatar's and participants' movements. After such exposure and compatible with a change in their off-line self-face representation, participants were more prone to recognize the avatar's face as their own, and this was also reflected in the activation of face-specific regions in the inferotemporal cortex. Further EEG analysis showed that the on-line sensory-motor effects during virtual mirror exposure caused these off-line visual effects, revealing the brain mechanisms that maintain a coherent self-representation, despite our continuously changing appearance.
Schizophrenia is a severe psychiatric disorder, in which patients experience an abnormal sense of self. While deficits in sensorimotor self-representation (agency) are well documented in schizophrenia, less is known about other aspects of bodily self-representation (body ownership). Here, we tested a large cohort (N = 59) of chronic schizophrenia patients and matched controls (N = 30) on a well-established body illusion paradigm, the Full Body Illusion (FBI). In this paradigm, changes in body ownership are induced through prolonged multisensory stimulation, in which participants are stroked on their back while seeing the stroking on the back of a virtual body. When the felt and seen stroking are synchronous, participants typically feel higher identification with the seen body as well as a drift in self-location towards it. However, when the stroking is asynchronous, no such changes occur. Our results show no evidence for abnormal body ownership in schizophrenia patients. A meta-analysis of previous work corroborates this result. Thus, while schizophrenia patients may be impaired in the sense of agency, their multisensory bodily self-representation, as tested here, seems to be unaffected by the illness.
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