If the avatar lags, it is not my own: Readiness potential as an objective biomarker of embodiment in virtual reality

The sense of embodiment—the subjective experience of owning and controlling one’s body—is crucial for self-awareness. Virtual Reality (VR) allows controlled manipulation of visuomotor synchrony to investigate embodiment. This study investigates how temporal discrepancies between real and avatar movements affect subjective embodiment and the Readiness Potential (RP), a neurophysiological marker of motor preparation. Using a VR “reach and press” task, participants ( n = 25 ) performed movements under three delay conditions (200, 400, 600 ms) and one condition with no added delay (NA-delay), while EEG (64-channel) recorded RP in anterior-frontal and central regions, and subjective embodiment was assessed via questionnaire. A control group performed the NA-delay condition in a real setting. Results showed that embodiment decreased with increasing delay (significant at 400 ms, 600 ms). RP peaks also diminished, particularly frontally, suggesting a shift from motor preparation to cognitive processes like error monitoring. sLORETA implicated dorsal anterior cingulate and prefrontal cortices in monitoring user-avatar discrepancies. These findings highlight RP as an objective biomarker for embodiment in VR. This offers significant implications for human–computer Interaction, providing a continuous, objective measure to improve user agency in VR, enhance neurorehabilitation therapies, optimize avatar design, and advance brain-computer interface systems. • Increasing visuomotor delay impairs the subjective sense of embodiment. • The frontal Readiness potential amplitude tracks avatar-user desynchrony. • Avatar lag shifts brain activity from motor preparation to cognitive processing. • RP provides an objective, real-time biomarker of embodiment in virtual reality.