Behavioral and neural effects of virtual embodiment in individuals with Body Integrity Dysphoria

Body Integrity Dysphoria (BID) is a condition characterized by a mismatch between an individual's physical body and their desired body state, often involving a desire for amputation. Virtual reality (VR) offers a non-invasive way to explore the effects of virtual embodiment on body ownership and sensorimotor integration. This study investigated the behavioral, phenomenal, and neurophysiological effects of embodying an amputated virtual body in three groups. Twenty individuals with BID (BID), 20 individuals with involuntary lower leg amputation or congenital limb absence (AMP), and 20 non-clinical controls (NCC) were exposed to an immersive virtual scene of a virtual body (complete or amputated) from a first-person (1 PP) or third-person perspective (3 PP) with synchronized visuomotor and visuotactile stimulation. Mu suppression (8-13 Hz) was assessed as marker for sensorimotor resonance using electroencephalography, alongside questionnaire-based assessments of body ownership and agency, as well as performance in a leg length estimation task. Individuals with BID reported significantly stronger ownership and agency over the amputated virtual body, particularly in the 1 PP condition. Mu suppression in 1 PP was (a) greater in BID than AMP, and (b) more pronounced when viewing an amputated body than a complete body across all groups. All participants estimated their leg as shorter after embodying the amputated avatar, reflecting a malleability in body schema following virtual embodiment. The findings demonstrate that virtual embodiment can significantly influence body experiences, the body schema, and neural activity. VR holds potential as a non-invasive tool for exploring body representation and could further provide therapeutic benefits for individuals with BID.