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: For Group 1 and 2 * 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 * Uncontrolled hypertension, hypotension, bradycardia, or tachycardia * History of baseline cardiac disease or atherosclerotic cardiovascular disease, including congestive heart failure, known severe coronary artery disease, severe carotid stenosis (e.g., bruits or history of TIA or stroke), or recent myocardial infarction (within 5 years). * Abnormal baseline electrocardiogram within last year * Previous vagotomy * Implanted metal cervical spine hardware, other metallic implants or implantable medical devices such as DBS * Active cancer * have previously had cancer in any areas where stimulation will occur * Documented abnormal cervical anatomy * History of brain tumor, aneurysm, bleed or head trauma * History of syncope or seizures (within the last 2 years) For Group 3 * Lack of decision-making capacity * Musculoskeletal or additional neurological conditions that negatively impact gait and balance * Spine or LE surgery within the past year