Neuroplasticity in Parkinson's Disease

Inclusion Criteria: Participants with PD * Diagnosis of idiopathic PD, as determined by a movement disorders neurologist in accordance with the PD Society Brain Bank diagnostic criteria * Not receiving levodopa or dopamine agonist to treat PD (at baseline) * Able to ambulate independently without the use of an assistive device (e.g. cane) for 50 meters Healthy Controls * Age- (+/- 3 years) and sex-matched to participants with PD * Able to ambulate independently without the use of an assistive device (e.g. cane) for 50 meters Exclusion Criteria: * Dementia diagnosis and/or a University of California Brief Assessment of Capacity to Consent (UBACC) score and MacCAT-CR score indicating impaired capacity to consent * History of musculoskeletal disorders that significant affect movement of lower or upper limbs as determined at the time of enrollment * History of bipolar disorder, post-traumatic stress disorder or major depressive disorder * Other significant neurological disorders that may affect participation or performance in the study * Implanted DBS or other neurosurgeries to treat PD * Pregnancy Additional exclusion criteria for TMS experiments (note that individuals who are excluded from the TMS experiment still have the opportunity to participate in the other data collection sessions): * History of seizures, epilepsy, stroke, multiple sclerosis, or traumatic brain injury * Recent history of frequent syncope (fainting) episodes in response to blood, emotional stress, or sensory triggers. * Intracranial metallic or magnetic devices (e.g. cochlear implant, deep brain stimulator) * Pacemaker or any implanted device * History of surgery on blood vessels, brain, or heart * Unexplained, recurring headaches or concussion within the last six months * Severe hearing impairment