Inclusion Criteria:  Diagnosis of Parkinson Disease Previously Untreated or treated for <4 weeks Mild to Moderate Parkinson disease (Hoehn & Yahr Stages I-II) About to start treatment with a L-Dopa preparation (Sinemet)  Exclusion Criteria:  The presence of other neurologic disease or findings on examination Depression: Geriatric Depression Scale score >11 Use of dopamine agonists or stimulants Evidence of a stroke or mass lesion on prior structural brain imaging (MRI or CT) Evidence of any confounding medical or psychiatric problem that would preclude task participation. Participants with cognitive impairment that might impair their capacity to provide informed consent.