Noninvasive VNS to Facilitate Excitability in Motor Cortex

Study Overview
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Brief Summary
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Transcranial Magnetic Stimulation (TMS) positively influences motor rehabilitation in stroke recovery. Transcutaneous auricular vagus nerve stimulation (taVNS) has shown effects on cortical plasticity. We investigate whether combination of TMS and taVNS is more effective at motor cortex excitability than either modality alone.

Detailed Description
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The investigators aim to determine the effects of taVNS on motor cortex excitability. The hypothesis is that taVNS alone (sham rTMS + active taVNS) will induce increases in motor cortex excitability (post-stimulation compared to baseline). The investigators expect these changes will be of a lesser magnitude than those of TMS alone (active rTMS + sham taVNS) due to the indirect mechanistic approach of taVNS. Another aim is to determine whether taVNS-paired TMS is more effective at inducing cortical excitability than TMS alone, as it is hypothesized that pairing two forms of neuromodulation (active rTMS + active taVNS) will increase TMS-induced cortical excitability in the motor cortex when compared to single modality approaches (active rTMS + sham taVNS; sham rTMS + active taVNS). Furthermore, it is expected that this increase is timing sensitive, and the paired approach will induce larger TMS-induced cortical excitability compared to unpaired neuromodulation (active taVNS + active taVNS).

Official Title
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Combining Transcutaneous Auricular Vagus Nerve Stimulation (taVNS) With Transcranial Magnetic Stimulation (TMS) to Enhance Cortical Excitability

Conditions
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Stroke, Stroke Sequelae, Motor Activity

Intervention / Treatment
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* Device: Transcranial Magnetic Stimulation
* Device: transcutaneous auricular vagus nerve stimulation (taVNS)


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Age 18-80 endorsing good health Exclusion Criteria: no TMS-induced motor cortex excitability changes in response to 20Hz motor cortex rTMS active psychiatric or neurological disorders history of CNS disease, concussion, overnight hospitalization, or other neurologic sequelae, tumors, seizures, frequent or severe headaches metal implanted above the neck currently taking seizure reducing medications currently taking psychotropic medications any psychotropic medication taken within 5 half-lives of procedure time abuse or dependence of drugs (excluding nicotine and caffeine) currently taking medications that lower the seizure threshold taking any of the stimulants, thyroid medication, or steroids implanted devices/ferrous metal of any kind history of seizure or seizure disorder inability to determine motor threshold. Pregnant females and children under the age of 18 will be excluded for safety reasons No vulnerable populations or special classes of subjects will be considered for participation.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 65 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Other
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Active taVNS, Active TMS<br> | Device: Transcranial Magnetic Stimulation<br>* transcranial magnetic stimulation delivers magnetic pulses to the brain through the scalp/skull<br>Device: transcutaneous auricular vagus nerve stimulation (taVNS)<br>* non-invasive vagus nerve stimulation delivers electricity to the ear<br>|
| Sham Comparator: Sham taVNS, Active TMS<br> | Device: Transcranial Magnetic Stimulation<br>* transcranial magnetic stimulation delivers magnetic pulses to the brain through the scalp/skull<br>Device: transcutaneous auricular vagus nerve stimulation (taVNS)<br>* non-invasive vagus nerve stimulation delivers electricity to the ear<br>|
| Sham Comparator: Active taVNS, Sham TMS<br> | Device: Transcranial Magnetic Stimulation<br>* transcranial magnetic stimulation delivers magnetic pulses to the brain through the scalp/skull<br>Device: transcutaneous auricular vagus nerve stimulation (taVNS)<br>* non-invasive vagus nerve stimulation delivers electricity to the ear<br>|
| Sham Comparator: Sham taVNS, Sham TMS<br> | Device: Transcranial Magnetic Stimulation<br>* transcranial magnetic stimulation delivers magnetic pulses to the brain through the scalp/skull<br>Device: transcutaneous auricular vagus nerve stimulation (taVNS)<br>* non-invasive vagus nerve stimulation delivers electricity to the ear<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Mean change of EMG-recorded Motor-evoked potential from baseline to immediately after intervention | The study uses Motor Evoked Potentials (MEPs), which are EMG measurements of a targeted movement (in other words, electromyography on the thenar muscles will sense a twitch that may occur due to motor cortex stimulation by TMS). The sensitivity of the motor cortex to stimulation is correlated to the degree of thumb twitch. This MEP will be used as a functional measure of changes in motor cortex excitability, as the amount of muscle twitch (MEP) should change if the cortex is more sensitive to TMS stimulation. The baseline measurement will be taken in the 60 seconds preceding the intervention; the intervention will last 20 minutes; post-intervention MEPs will be measured at 1, 5, 10, 15, and 20 minutes following the end of the intervention. | Every 5 minutes up to 20 minutes following intervention end | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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stroke, recovery, TMS, VNS, motor, motor cortex