Noninvasive Vagus Nerve Stimulation (VNS) for Neuromotor Adaptations
Condition: Healthy Young Adults
Study type: Interventional

Summary: 
      The study will examine how electrical stimulation of vagus nerve (i.e. nerve around the outer
      ear) from the skin surface during motor training influences a brain hormone (called
      norepinephrine), brain activity, and motor performance.
    

Detailed description: 
      Motor function is compromised with advanced age, and motor impairment is involved in various
      neuromotor injuries and disorders including stroke, spinal cord injury, amputation, and
      aging. Development of effective interventions for facilitating neuromotor adaptation is
      essential for accelerating or augmenting rehabilitation outcomes in the control of impaired
      limbs. The ultimate goal of the study is to find non-pharmacological and non-invasive
      neuromodulating interventions for enhancing the rehabilitation outcomes that may be applied
      to individuals with impaired motor function. In rats, implanted afferent vagus nerve
      stimulation paired with motor training enhanced neuromotor adaptation and motor recovery most
      likely through increased release of central neuromodulators that originate from the
      brainstem. The investigators propose to translate the findings in rats into humans by
      applying vagus nerve stimulation noninvasively. Transcutaneous VNS (tVNS) can noninvasively
      activate the brainstem including locus coeruleus, where norepinephrine (i.e. neuromodulator)
      is synthesized. However, it is unknown whether tVNS leads to increasing neuromodulators and
      facilitating neuromotor adaptations when combined with motor training in humans. With
      potential applicability of this novel intervention for facilitating neuromotor adaptation to
      various clinical human populations in future scope, it is essential to start with the basic
      understanding about the effect of tVNS on the neuromotor system and training-induced
      adaptation in neuromotor behavior in non-disabled humans. The overarching hypothesis is that
      an application of tVNS increases central norepinephrine and facilitates training-induced
      neuromotor adaptations in humans. The specific aim is to examine the effect of tVNS on
      central norepinephrine and training-induced neuromotor adaptations in humans. The effect of
      applying tVNS concurrently to visuomotor training will be investigated by comparing the
      changes in central norepinephrine and changes in the visuomotor skill and corticospinal
      excitability due to training with and without tVNS (sham) in non-disabled humans. The
      visuomotor skill will be assessed with the root-mean-square error of the produced force
      against the target force, which will be normalized to the maximal voluntary contraction force
      (MVC) . The investigators expect that subjects with concurrent tVNS during training show
      greater increases in the visuomotor skill and corticospinal excitability after training. The
      investigators also expect that tVNS increases central norepinephrine, and the amount of
      neuromotor adaptations due to training is associated with that of tVNS-induced increase in
      central norepinephrine. These expected findings will be the first evidence on the efficacy of
      concurrent tVNS with motor training for upregulating central norepinephrine and facilitating
      training-induced neuromotor adaptations in humans. They will open new scientific and clinical
      fields of study that will lead to the creation of motor rehabilitation paired with tVNS that
      can enhance rehabilitation outcomes in individuals with motor impairment. Demonstration of
      associated changes between central norepinephrine and neuromotor adaptations due to tVNS in
      non-disabled humans is a necessary step for applying tVNS to rehabilitation with the
      understanding of the underlying mechanism and for potentially using central norepinephrine as
      a predictor of tVNS efficacy in rehabilitation.
    

Intervention name(s): tVNS; Motor training
Intervention type(s): Other; Other
Intervention description(s): Intervention; Same finger training for both arms
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Double (Participant, Investigator)
Primary purpose: Basic Science
Keywords: tVNS, training, neuromotor adaptation