Bodily-self representation and its alterations in pathological conditions: insights from eating disorders, borderline personality disorder and sensorimotor disturbances

Bodily-self representation (BSR) is the ability to represent our own body as distinct from other people and from the environment. Body ownership (the feeling that one’s own body belongs to oneself), sense of agency (the experience of being the author of one’s own actions), and bodily-self recognition contribute to the emergence and normal functioning of BSR. Literature has described how BSR can be selectively disrupted by pathological conditions. Eating Disorders (EDs) and Borderline Personality Disorder (BPD) offer a unique opportunity to study BSR, being its alterations at the root of their psychopathology. Sensorimotor disturbances such as Phantom Limb Sensation (PLS) allow the examination of how sensorimotor illusions may impact on BSR. This thesis provides an experimental account of BSR and its alterations, discussing behavioral and neurophysiological evidence. In EDs, BSR alterations were examined across three studies. Using the Rubber Hand Illusion in its visuo-tactile and visuo-motor versions, we probed sense of body ownership and sense of agency, revealing a abnormal agency even in absence of voluntary movements. A second study showed that implicit self-identity recognition depended on body misperception: when a mismatch between actual and perceived body- image was present, individuals failed to recognize their own body in its actual dimensions describing body misperception as a transdiagnostic factor. A third study extended these findings at the neurophysiological level, showing absence of the typical neural marker of bodily-self recognition in women with high body misperception. In BPD, altered sense of agency emerged when active movements were required, and dissociative symptoms and self-harming behavior played a crucial role: patients engaging in self-harm exhibited a spared BSR compared to those who did not. Finally, a behavioral and neurophysiological paradigm was developed to address illusory agency in moving phantom limb. Perceiving biological apparent movements recruits action observation networks, relying on motor resonance. Overall, findings highlight the interplay between acting and sensory self as crucial for a coherent BSR.