Virtual, augmented and mixed reality for motor neurorehabilitation: a scoping review focused on the role of body representation

Background: In neurorehabilitation, virtual reality (VR) applications cover a wide range of areas, including the rehabilitation of patients with various types of brain and spinal cord injuries. VR provides the subject multisensory feedback, enhancing neuronal plasticity within the sensorimotor cortex. Objective: The systematic review critically analyses the existing literature on VR applications related to motor problems and somatic representation to propose new tools and experiments. Methods: The Protocol was registered in the international database for systematic reviews PROSPERO (ID: 481092 - 22 November 2023). The review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Guidelines. To implement the search string, a broad overview of previous literature reviews in the field was developed. The databases PubMed, Embase, Scopus, and Web of Science (7 December 2023) were explored, and data regarding study design, methodology, participant characteristics, specific devices and instruments used and tested, body representation, and virtual somatic embodiment were collected. The Newcastle-Ottawa Scale was used to assess the methodological quality of the studies; for case report studies, a dedicated scale was used. Results: The review included 26 studies, mainly clinical trials on neurological patients. Internationally, VR technologies in the period 2008-2023 have evolved significantly; the emergence of inexpensive devices such as Oculus Rift and HTC Vive has stimulated research in this area. The best results have been achieved for patients with sensorimotor deficits. In VR systems, users experience a first- or third-person view (where their avatar is present) of the synthetic world around them. All included studies used the first-person perspective, which was found to be most effective. Five studies incorporated EEG for recording brain responses during experiments, while two studies used transcranial stimulators to enhance the effect of the VR intervention. A couple of studies employed other kinds of devices, such as eye trackers. Regarding the 3D engine used, Unity 3D remains the preferred choice for the development of VR applications in research due to its ease of learning and seamless integration with devices. Conclusions: The review of the selected studies shows that the use of VR devices enhances reinforcement learning, thereby improving motor and cognitive recovery. The emerging operational proposition supports the use of tailor-made techniques in the rehabilitation setting - aimed at improving and evaluating the outcomes of therapeutic interventions in the treatment of neurological patients. Clinical Trial: International database for systematic reviews PROSPERO, ID: 481092 - 22 November 2023.