Can familiarization with a supernumerary robotic finger restore task-dependent cortico-autonomic coupling in first-time healthy users?

Supernumerary Robotic Fingers (SRFs) have proven their capabilities in enhancing manipulation and dexterity in precision tasks enabling multitasking in healthy individuals, while also playing a compensatory role for those with motor impairments. However, the literature on SRF adaptation and embodiment remains scarce, particularly in terms of the neurophysiological basis underlying their introduction, use, and assimilation. This study employed a controlled-time-delay-stability (CTDS) framework to investigate physiological embodiment by capturing multimodal signals (encephalography (EEG), electrodermal-activity (EDA), photoplethysmography (PPG), and respiratory) in 30 adults performing three activities-of-daily-living. Tasks were completed across three phases: without SRF, with SRF immediately after attachment, and with SRF following individualized training. CTDS quantified pairwise strength and directionality of dynamic interactions while controlling for indirect effects. Network visualization provided a holistic view of brain–body reconfiguration with SRF use. Resting baselines showed no significant differences across phases, suggesting SRF attachment alone did not introduce sufficient stress to alter brain–body interactions. During tasks, brain–body interactions exhibited task-dependent modulation. This modulation was suppressed with initial SRF attachment but reappeared after training/familiarization, with post-training patterns becoming statistically indistinguishable from those without the SRF. These results indicate that SRFs can be effectively embodied into the body schema after targeted training. The transient plasticity observed in first-time users may serve as a biomarker for customizing SRF training and tracking neurorehabilitation progress. Extending prior findings of rapid cortical adaptation, this study shows that brain–body networks reconfigure in a task-specific manner toward assimilation following brief familiarization. Future work warrants clinical validation and translation.