Task-specific cortical mechanisms of taVNS-paired task-oriented training for post-stroke upper extremity dysfunction...

Area of Science:

• Neuroscience
• Rehabilitation Medicine
• Biomedical Engineering

Background:

• Upper limb dysfunction is a common and debilitating consequence of stroke.
• Task-oriented training (TOT) is a cornerstone of stroke rehabilitation, but its efficacy can be modulated by cognitive load.
• Transcutaneous auricular vagus nerve stimulation (taVNS) is an emerging non-invasive neuromodulation technique with potential to enhance neuroplasticity and motor recovery.

Purpose of the Study:

• To investigate the cortical task-specific response patterns underlying upper limb functional improvement in stroke patients.
• To evaluate the efficacy of transcutaneous auricular vagus nerve stimulation (taVNS) combined with task-oriented training (TOT) under varying cognitive loads.
• To analyze neurophysiological and brain imaging changes associated with taVNS-augmented rehabilitation.

Main Methods:

• A randomized, double-blinded, sham-controlled trial involving 30 subacute stroke patients.
• Intervention groups received either active taVNS or sham stimulation concurrently with 3 weeks of TOT.
• Clinical assessments (FMA-UE, MoCA, FSS, MBI), neurophysiological measures (HRV, MEPs), and functional near-infrared spectroscopy (fNIRS) under varying cognitive loads were performed pre- and post-intervention.

Main Results:

• The taVNS group showed significantly greater improvements in heart rate variability (HRV) indices and clinical scores (FMA-UE, MoCA, MBI, FSS) compared to the sham group.
• taVNS enhanced corticospinal excitability, evidenced by improved ipsilesional motor-evoked potential (MEP) elicitation rates and reduced contralesional MEP latency.
• fNIRS revealed altered brain activation patterns and functional network connectivity in the taVNS group, particularly in prefrontal and sensorimotor regions during cognitive-motor tasks.

Conclusions:

• taVNS paired with TOT enhances autonomic homeostasis, corticospinal excitability, and task-specific cortical activation in stroke patients.
• This neuroregulatory approach promotes improved cognitive-motor integration and facilitates upper limb functional recovery.
• The findings suggest taVNS is a promising adjunct therapy for stroke rehabilitation, particularly for improving executive control in complex tasks.