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.

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).

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.

No plan to share data except through peer-review.

Up to 8 months

There are no adverse events reported in this study.