Quantifying Prosthetic Embodiment: Interactions Between Agency, Ownership, and Peripersonal Space in a Closed-Loop Sensorimotor Task

Introduction Embodiment refers to the combined feelings of owning one's body (sense of ownership, SoO), controlling its actions (sense of agency, SoA), and being situated in space within it (self-location or peripersonal space, PPS). This concept is increasingly relevant to emerging bionic prosthetic systems, which offer naturalistic control and sensory feedback experienced as originating from the missing limb. Although these constituent components are interrelated, a unified understanding of their dynamic relationships in upper-limb prostheses remains limited. This study investigated how sensorimotor cues modulate the components of embodiment and explored relationships between explicit and implicit measures during the operation of a prosthesis-like system. Methods Twenty-three able-bodied participants performed grasping tasks with a prosthesis-like robotic hand while sensorimotor cues and the hand’s spatial position were varied. We assessed explicit ratings of SoO and SoA, intentional binding (the perceived temporal compression between action and outcome), and proprioceptive drift (the shift in perceived hand location toward the prosthesis-like system). Statistical modeling and correlation analyses were conducted across these metrics to quantify interactions among embodiment components. Results All embodiment measures-explicit SoO, explicit SoA, intentional binding, and PPS-were significantly higher during congruent tactile feedback with voluntary control compared to control conditions without feedback and voluntary control. Explicit SoO averaged 0.98 ± 0.05 (p = 0.858 vs. cut-off score), SoA averaged 2.07 ± 0.04, intentional binding showed a time compression of -97.83 ± 10.17 (ms), and PPS extended to 5.7 ± 0.68 (cm) (\(p < 0.05\) for all vs. control conditions). Explicit SoO positively correlated with explicit SoA (r = 0.70) and intentional binding (r = 0.56), but not with PPS (r = -0.03), suggesting that self-location may be an independent phenomenon. Intentional binding generally complemented explicit SoA yet diverged under sensory-motor mismatched conditions, highlighting a partial dissociation between explicit agency and its implicit intentional binding counterpart. Conclusion We demonstrated that SoO, SoA, and PPS can be independently modulated by systematically manipulating sensorimotor cues in a prosthesis-like system. Given the variability of all measures of embodiment, our results indicate that embodiment is not a binary phenomenon but a fluid, emergent experience shaped by interdependent processes that are selectively influenced by specific sensorimotor cues.