Based on studies showing better responsiveness of motor versus cognitive symptoms to Parkinson's Disease medication, also known as dopaminergic treatments, the investigators hypothesize that comparison of resting state networks in the on versus off medication state in Parkinson's Disease patients will show greater effects on brain networks associated with motor control.

Subject participation includes two 25-30 minute MRI scans. The subject will arrive in the "off" state (PD medications withheld for approximately 12 hours prior to the scan). Following the initial scan, the subject will receive 125% of his or her usual daily morning dose of PD medications which is calculated as levodopa dose equivalents (LDE) and is given as carbidopa-levodopa. The subject will then wait for an hour allowing for the medication to begin working. During this time the subject will complete cognitive assessments, questionnaires regarding the history and current state of PD, and motor assessments. The subject will then undergo a second MRI scan of approximately 25-30 minutes. The subject after completing the second MRI scan is free to leave. The entire study is approximately 2 and 1/2 hours long.

Inclusion Criteria:

• Idiopathic Parkinson's Disease (PD)
• Older than 30 years of age at the time of diagnosis
• Hoehn and Yahr stage greater than or equal to 2.5
• PD duration greater than 3 years
• Stable regimen of PD medications for at least 2 weeks prior to imaging
• PD medications include carbidopa-levodopa

Exclusion Criteria:

• Patients with a diagnosis of other neurodegenerative conditions
• Patients unwilling or unable to give informed consent
• Contraindications (cardiac pacemaker, etc.) or inability (e.g., claustrophobia) to undergo MRI scan

Patients with Parkinson's disease on dopaminergic therapy.