SELF-UNITY · The Unity of the Bodily Self

How do we come to experience ourselves as single physical entities? Under normal healthy conditions, we humans always experience a single body as our own physical self, and this bodily self is undivided and perceived as a single whole. But what cognitive processes and brain mechanisms mediate this unity of the bodily self? This fundamental question has long been beyond the reach of experimental studies because of the lack of behavioral paradigms that allow controlled manipulation of basic components of the self-unity. To address this issue, we here propose the use of novel full-body illusion paradigms to “fragment”, “duplicate” or “split” the sense of bodily self during well-controlled behavioral and neuroimaging experiments. By studying the behavioral and neural principles that determine specific illusory changes in perceived self-unity, we can elucidate much about the neurocognitive mechanisms that support the sense of having a single unitary bodily self under normal conditions. Our pioneering behavioral paradigms utilize the newest virtual reality technologies, and these are combined with multimodal neuroimaging using the most advanced analysis methods, such as multivariate pattern recognition. The aims of the project are to unravel (i) how we come to experience a single bodily self as opposed to multiple ones; (ii) how we perceive a coherent bodily self instead of fragmented parts; and (iii) how information from different sensory modalities – including vestibular and interoceptive signals – are integrated to achieve this coherent sense of a singular bodily self. The new basic knowledge generated by this project will be important for future clinical neuroscience research into major psychiatric and neurological disorders with disturbances in self-unity, such as schizophrenia, dissociative disorders and stroke with body neglect, by providing novel ideas for hypotheses about the involved neurocognitive pathophysiology.