A methodological study of virtual self-touch: effects on perception and motor control strategies.

Introduction: Advances in virtual reality technology have facilitated research that leverages the plasticity of body schema. This study investigates whether the use of an avatar habituation method, in which participants voluntarily touch an avatar as a substitute body and receive haptic feedback, is crucial for updating body schema. This approach is called virtual self-touch (VST). Methods: We conducted an experiment with 10 participants using avatars that were the same size as the participants' actual bodies and with the length of the right forearm increased by 1.5 times. The effectiveness of VST was evaluated using questionnaire-based sense of body ownership and agency, proprioceptive drift measurements, and reaching tasks without displaying the avatar. Further, the proposed method was compared with an existing avatar habituation method, the arm swing task (AST). Results: Our results demonstrated that VST produced larger changes in proprioceptive drift than AST. Furthermore, larger variations in the fingertip trajectories and reach endpoints were observed for VST than for the AST during the reaching task, which indicated that VST affects motor planning. Discussion: This suggests that VST contributes to changes in the body schema. Additionally, distortions in spatial perception were detected in the environment when only somatosensory feedback was relied on. This result provides insights about the representation of spatial perception in the body schema.