Electrophysiological Evaluation of Mirrored Hand Movements in Virtual Reality: A Proof of Concept for Virtual Mirror Therapy

Observing the movement of the affected hand by virtually mirroring the healthy hand's movement has been reported to accelerate motor rehabilitation. To investigate the underlying neurophysiological mechanisms, we recorded electroencephalograms (EEG) of fifteen healthy volunteers, who performed a center-out reaching task with their non-dominant hand while they saw the avatars of either the moving or the mirrored hand in an immersive virtual reality (VR) environment. The event-related potentials (ERP) and oscillations (ERO) time-locked to either the stimulus-cued initiation (sReach) or the finishing time point of the reaching trial (fReach) were compared between the direct and mirrored conditions. In sReach, a P3 wave was observed with larger amplitude on the motor areas controlling the mirrored hand (p = 0.01), while the amplitude of a negative potential shift preceding fReach time point, the reaching-related negativity (RRN), was also larger in the mirrored condition (p = 0.009). Finally, EROs in the theta, alpha, and beta frequency bands significantly differed between the two conditions (all p < 0.05) with scalp topographies pointing to either the activation of the motor areas controlling the mirrored hand or visuo-spatial attention system due to the incongruent visuomotor feedback in immersive VR. The results provide electrophysiological evidence for adaptive control processes underlying mirror therapy and extend classical models of movement-related EEG signals, offering a mechanistic bridge between virtual feedback and functional neurorehabilitation.