Non-invasive VNS for Parkinson's Gait

Inclusion Criteria: * Parkinson's disease, as diagnosis by a VA neurologist * HY stages 2-3 * Self-report Freezing of Gait * Able to ambulate for 2-min without an assistive device * Parkinson's disease medications are stable for 4-weeks and expected to be on stable medications for duration of the study Exclusion Criteria: * Lack of decision-making capacity * Prescribed centrally acting anticholinergics (e.g., amitriptyline) or cholinesterase inhibitors * Musculoskeletal or additional neurological conditions that negatively impact gait and balance * Spine or LE surgery within the past year * Known or suspected: * severe atherosclerotic cardiovascular disease * severe carotid artery disease * congestive heart failure * known severe coronary artery disease or prior myocardial infarction * Abnormal baseline electrocardiogram within last year * Previous vagotomy * Implanted metal cervical spine hardware, other metallic implants or implantable medical devices such as DBS * History of syncope or seizures (within the last 2 years)