Transcutaneous Auricular Vagus Nerve Stimulation during Movement Selectively Activates Motor Circuitry without...

Area of Science:

• Neuroscience
• Rehabilitation Medicine
• Neuromodulation

Background:

• Transcutaneous auricular vagus nerve stimulation (taVNS) is a non-invasive neuromodulation technique with therapeutic potential.
• Its application in neurorehabilitation is growing, but its effects during active movement are poorly understood.
• Most studies investigate taVNS at rest, neglecting the dynamic neural activity during movement.

Purpose of the Study:

• To investigate the neurophysiological basis of pairing taVNS with movement.
• To determine if taVNS enhances motor circuitry during active movement.
• To identify state-dependent effects of taVNS on neural and autonomic systems.

Main Methods:

• Thirty-six healthy adults participated in two experiments.
• Experiment 1: Assessed autonomic, neuromodulatory, and cortical responses to taVNS during movement and stillness using EEG, HR, and GSR.
• Experiment 2: Evaluated corticospinal excitability via TMS-induced motor evoked potentials (MEPs) during taVNS.

Main Results:

• taVNS increased TMS-induced MEP amplitudes, indicating transient corticospinal output facilitation when coinciding with motor engagement.
• EEG sensorimotor activity was enhanced by taVNS during movement but not stillness.
• Pupil diameter showed a state-independent response to taVNS, while autonomic indices were not significantly modulated beyond movement-related changes.

Conclusions:

• taVNS preferentially boosts task-engaged motor circuitry in a state- and time-dependent manner.
• This provides mechanistic support for pairing taVNS with movement in neurorehabilitation protocols.
• Pupil diameter, EEG, and MEPs serve as sensitive biomarkers for phasic taVNS effects.