| Objective:To observe the immediate effects of transcutaneous auricular vagus nerve stimulation (taVNS) on the brain activation pattern of patients with unilateral upper limb motor dysfunction complicated by stroke during active grasping task by using functional near-infrared spectroscopy (fNIRS), and to explore the mechanism of the brain network that facilitates the recovery of upper limb function. Methods: Totally, 30 eligible stroke patients were randomly divided into 15 cases each in the taVNS group and the Sham group, and heart rate variability (HRV) was measured before and after the intervention in both groups. After the first HRV test, a 5-min resting state fNIRS test was performed in both groups, followed by continuous true/false taVNS stimulation in both groups, during which a second 5-min resting state fNIRS test was performed, and then the patients were instructed to complete a 20-set active grasping task for a total of 700 s, while a third fNIRS test was performed. Results: HRV results showed that the low-frequency/high-frequency power ratio (LF/HF) was significantly lower in the taVNS group than in the Sham group (P<0.05). Significant activation of the affected premotor and supplementary motor area (pSMA), sensory-motor cortex (SMC)，the unaffected dorsolatoral prefrontal cortex（DLPFC）and bilateral orbital frontal cortex（OFC）was observed in the taVNS group (P<0.05). A network-based statistical method (NBS) analysis showed that taVNS significantly enhanced the functional connectivity between the affected side PFC and the non-affected side PFC,the affected side SMC and the non-affected side PFC, and the node clustering coefficients and local efficiencies of OFC on the affected side were significantly higher (P<0.05). The taVNS group showed an increase in the global shortest path length of the functional network of the brain, and a decrease in the global efficiency (P<0.05). Conclusion: Immediate taVNS regulates bilateral prefrontal and motor cortex networks by activating the frontal-vagus pathway, thus promoting the activation and functional reorganisation of the relevant brain regions, which may be its key mechanism to promote the recovery of the upper limb. |
