Exploring the Role of Parietal Transcranial Magnetic Stimulation on Embodiment-Related Processes During Virtual Prosthesis Control

Despite advancements in bionic technology, disrupted afferent and efferent pathways in individuals with limb loss may hinder prosthetic embodiment. Transcranial Magnetic Stimulation (TMS) has emerged as a promising tool for investigating and modulating sensorimotor processes, though its application in neurorehabilitation for individuals with limb differences remains limited. This pilot study explores whether TMS over parietal regions associated with the grasping-function and motor planning can enhance the sense of embodiment and influence motor behaviour. In this feasibility protocol, six healthy participants and two prosthesis users underwent a virtual reality TMS-training protocol. Its effects were assessed through pre- and post-training evaluations using standard self-reported embodiment surveys, functional performance metrics, and a Locus of Attention Index. Participants completed two assessments without TMS, before and after a training session with TMS. Additionally, one final assessment with TMS was conducted, designed to evaluate its direct impact on performance metrics. Results in healthy participants indicate that while TMS did not significantly alter the perceived embodiment, it affected the visual attention allocation. Additionally, trajectory velocity differed between no-TMS and TMS assessments. Finally, the online system evaluation on two prosthesis users highlights the feasibility of applying parietal TMS in training for prosthetic embodiment research, warranting further investigation with larger and more comprehensive samples to better establish the role of TMS in sensorimotor rehabilitation with amputees.