Effect of Immersive Virtual Mirror Visual Feedback on Mu Suppression and Coherence in Motor and Parietal Cortex in Stroke

Abstract Background: This study aimed to investigate the activation pattern of the motor cortex (M1) and parietal cortex during immersive virtual reality (VR)-based mirror visual feedback (MVF) of the upper limb in patients with chronic stroke. Methods: Fourteen patients with chronic stroke with severe upper limb hemiparesis (Brunnstrom stage of hand 1-3) and 21 healthy controls were included. The participants performed wrist extension tasks with their unaffected wrists (or the dominant side in controls). In the MVF condition, the movement of the affected hand was synchronized with that of the unaffected hand. In contrast, only the movement of the unaffected hand was shown in the no-MVF condition. Electroencephalography was obtained during experiments with two conditions (MVF vs no-MVF). Mu suppression in the bilateral M1 and parietal cortex and mu coherence between the ipsilateral M1 and parietal cortex in each hemisphere and interhemispheric M1 were used for analyses. Results: In patients with stroke, MVF induced significant mu suppression in both the ipsilesional M1 and parietal lobes (p=0.006 and p=0.009, respectively), while significant mu suppression was observed in the bilateral M1 (p=0.003 for ipsilesional and p=0.041 for contralesional M1, respectively) and contralesional (contralateral hemisphere to the moving hand) parietal lobes in the healthy controls (p=0.036). The ipsilesional mu coherence between the M1 and parietal cortex in patients with stroke was stronger than that in controls regardless of MVF condition (p<0.001), while mu coherence between interhemispheric M1 cortices was significantly weaker in patients with stroke (p=0.032). Conclusion: In patients with stroke, MVF using immersive VR induces mu suppression in the ipsilesional M1 and parietal lobe. Our findings provide evidence of the neural mechanism of MVF using immersive VR and support its application in patients with stroke with severe hemiparesis.