Neural Oscillatory Dynamics in Joint Action: Dissociable Roles of Entrainment and Beta Modulation in Self-Other Integration.

Temporal coordination is fundamental for human communication and collaboration, yet the underlying neural mechanisms remain poorly understood. Central to this process is self-other integration, defined here as the extent to which a partner is processed as self-relevant and incorporated into one's sensorimotor representations. Recent evidence suggests that beta-band oscillatory dynamics may provide a shared sensorimotor framework supporting such integration. Here, we leveraged an immersive virtual-reality body-swap illusion to experimentally manipulate the embodiment of a partner's hand during joint rhythmic action, thereby testing the sensitivity of oscillatory brain dynamics to distinct levels of self-other integration. Forty participants, paired into 20 dyads, performed a finger-tapping task while viewing either their partner's hand in first-person (1P) or second-person (2P) perspective, or their own hand in uncoupled control conditions. Electroencephalography hyperscanning demonstrated that both neural entrainment of low-frequency oscillations and beta modulation linked to partner-generated movements occurred in visually coupled conditions. However, only beta modulation was selectively enhanced when participants perceived their partner's hand from a 1P perspective. These findings suggest that while neural entrainment reflects a general mechanism for tracking a partner's rhythmic behavior, beta modulation specifically supports the integration of the other's effector into one's bodily representation.