A sense of losing one's hand induced by visuotactile conflict in virtual reality.

Embodiment of external objects has been widely studied to elucidate the underlying mechanisms of human body perception, whereas disembodiment has received only limited attention despite its importance. To address this gap, we designed a sensorimotor feedback paradigm using virtual reality to induce bodily disappearance, referred to here as the sense of body loss. Participants wearing a head-mounted display moved a virtual right hand-synchronized with their real right hand-to repeatedly touch the index finger of a virtual left hand. Two factors were manipulated during the experiment: spatial congruency between the real and virtual right hands (overlapped vs. displaced) and visual contact between the virtual index fingers (visually touch-enabled vs. visually touch-disabled). Participants first completed a baseline trial (overlapped & visually touch-enabled condition) involving physical contact between their real index fingers, followed by one of the remaining three conditions without physical contact. Subjective experiences were assessed using a questionnaire, and the trajectory and proprioceptive drift (PD) of the right index finger were measured. Participants reported a pronounced sense of body loss and sensory attenuation in the displaced & visually touch-enabled condition, accompanied by greater PD and unconscious movements of the left index finger. These results suggest that visuotactile conflict during virtual self-touch can induce a sense of body loss.