A Closed-Loop ta-VNS System Synchronized with BCI-Based Motor Training for Post-Stroke Upper Limb Rehabilitation.

Transcutaneous auricular vagus nerve stimulation (ta-VNS) involves applying electrical stimulation via electrodes to the auricular concha. This activates vagal afferent fibers, initiating an ascending pathway from the periphery to the brainstem, which ultimately stimulates central vagal projections and promotes neural plasticity. Previous studies have demonstrated that combining ta-VNS with motor training offers synergistic benefits for motor recovery after stroke. However, these combined approaches typically employ open-loop stimulation with fixed parameters, lacking real-time closed-loop responsiveness to dynamic neural activity. To address this limitation, we developed a novel closed-loop ta-VNS system synchronized with electroencephalography (EEG)-triggered brain-computer interface (BCI) motor training. This system was designed to enhance corticospinal coupling and promote synaptic plasticity. We established a standardized protocol for applying this closed-loop ta-VNS system synchronized with BCI-based motor training in stroke patients. Using EEG-based functional assessment, we compared the effects of the closed-loop ta-VNS system synchronized with BCI-based motor training to those of sham ta-VNS synchronized with BCI-based motor training. This work provides the methodological and theoretical groundwork for the clinical application of this approach in stroke rehabilitation.