People with Parkinson disease commonly experience difficulty driving, which requires the arms and legs to do different tasks simultaneously. Driving difficulties can lead to isolation, depression, loss of independence and mobility, and increased incidence of car accidents. Through understanding the impact of Parkinson disease on mechanisms underlying attention and multi-limb control, training and rehabilitation programs can better focus on the needs of drivers with Parkinson disease. The proposed study aims to address this need by taking measures of simulated driving at one point in time. Subjects with PD are tested at a single time point when they are at their "best" point in their day and on another day when they are at their worst and are about to take their next dose of medication. Healthy age-matched subjects are not taking anti-parkinson medication so are tested at only one point.

Inclusion Criteria:

• have a clinical diagnosis of mild to moderate idiopathic PD (Hoehn & Yahr stages 1-3),
• hold a valid driver's license and drive at least once a week, and
• be capable of providing informed consent and complying with study procedures. Control group participants will be healthy, neurologically intact individuals, age-matched to within 2 years of the PD subjects.

Exclusion Criteria:

• impaired global cognition (i.e., a score of < 20 on the Montreal Cognitive Assessment (MoCA) screening tool)
• sensory loss in the lower limb as assessed by clinical test of vibration perception at the ankle,
• orthopedic, visual, or neurological conditions that would prevent performance of the experimental tasks,
• inability to complete and pass the assessment testing,
• history of neurological illness such as head trauma, previous stroke, epilepsy, demyelinating disease, or
• complicating medical problems such as diabetes.

Individuals will be recruited through collaboration with hospitals, clinics, physical therapy centers, private practice physicians and physical therapists, neurology-based fitness centers, community centers, PD support groups, online trial-matching services (e.g., FoxTrialFinder.michaeljfox.org), word of mouth, and advertising. Recruitment will be limited to the greater Phoenix metropolitan area.

It is not yet known if there will be a plan to make IPD available. Institutional infrastructure being developed.