Brain cortical activation and functional connectivity during the integration of virtual reality with action observation and motor imagery: a functional near-infrared spectroscopy study

Virtual reality (VR) is a technology integrable with traditional rehabilitation therapies that has been clinically applied. When combined with action observation (AO) and motor imagery (MI), VR potentially offers an alternative treatment for movement-impaired patients (e.g., post-stroke, spinal cord injury). However, research on VR combined with AO and MI (VRAO and VRMI) is insufficient, and studies have not yet validated effectiveness or explored the related brain mechanisms. Using functional near-infrared spectroscopy (fNIRS) synchronized with three tasks—VRAO, VRMI, and physical walking—this study dynamically evaluated prefrontal cortex activation and functional connectivity in 39 healthy adults. Pairwise comparisons revealed significantly greater ΔHbO during walking versus VRAO and VRMI (p < 0.05). This differential weakens in β-value comparisons, where VRAO exhibited SMA and M1 β values comparable to walking (p > 0.05), while other regions and VRMI showed significantly reduced values (p < 0.05). In brain network analysis demonstrated stronger homologous and heterologous connectivity during VRAO and VRMI versus walking, with VRMI specifically strengthening bilateral DLPFC, FPA, S1, M1, PM&SMA heterologous connections (p < 0.001). Regarding brain activation, while the local effects of VRAO were comparable to walking, both VR tasks showed significantly lower hemodynamic responses. Conversely, VRAO and VRMI induced cognitive-motor network synergies stronger than physical walking. With ongoing VR technology advancements, VRAO and VRMI will demonstrate substantial refinement potential as emerging alternative therapies for brain rehabilitation.