To determine whether treatment with transauricular vagus nerve stimulation (taVNS) during the training of an affected upper limb of a patient with chronic stroke on a robotic motor task alters the motor impairment.

The investigators will evaluate whether transauricular vagus nerve stimulation (taVNS) delivered during extensor movements executed on a robotic device will alter the clinical measurement of upper limb motor performance in 45 patients with chronic stroke.

Patients will engage the robot first with their unaffected limb. This practice will ensure understanding and serve to activate the hemisphere ipsilateral to the impaired limb. Patients are likely to perform this activity quickly, there will not be any taVNS during this part of the procedure. Patients will then wear the taVNS device on the left ear for the duration of the subsequent phase of the robotic training. During this phase the patient will engage the robotic device with the affected limb and complete the protocol and the stimulation or sham stimulation will occur with every extensor movement.

Inclusion Criteria:

• In receipt of full vaccination status and no recent upper respiratory symptoms and no loss of taste or olfaction.
• Individuals between 18 and 85 years of age
• First single focal unilateral supratentorial ischemic stroke with diagnosis verified by brain imaging (MRI or CT scans) that occurred at least 6 months prior
• Cognitive function sufficient to understand the experiments and follow instructions (per interview with Speech Pathologist or PI)
• Fugl-Meyer assessment 12 to 44 out of 66 (neither hemiplegic nor fully recovered motor function in the muscles of the shoulder, elbow, and wrist).

Exclusion Criteria:

• Recent fever or upper respiratory symptoms.
• Botox treatment within 3 months of enrollment
• Fixed contraction deformity in the affected limb
• Complete and total flaccid paralysis of all shoulder and elbow motor performance
• Prior injury to the vagus nerve
• Severe dysphagia
• Introduction of any new rehabilitation interventions during study
• Individuals with scar tissue, broken skin, or irremovable metal piercings that may interfere with the stimulation or the stimulation device
• Highly conductive metal in any part of the body, including metal injury to the eye; this will be reviewed on a case by case basis for PI to make a determination
• Pregnant or plan on becoming pregnant or breastfeeding during the study period
• Significant arrhythmias, including but not limited to, atrial fibrillation, atrial flutter, sick sinus syndrome, and A-V blocks (enrollment to be determined by PI review)
• Presence of an electrically, magnetically or mechanically activated implant (including cardiac pacemaker), an intracerebral vascular clip, or any other electrically sensitive support system; Loop recorders will be reviewed on a case by case basis by PI and the treating Cardiologist to make a determination

The patient will not know whether they are receiving taVNS, all patients will feel a tingling in the ear as the current is ramped up and then down to determine a stimulation threshold, but only the active group will receive timed stimulation bursts during the robotic protocol that engages the affected limb. The measuring clinician will not know a patient's group assignment.