Other exclusion criteria include presence of atypical parkinsonism syndromes due to drugs (e.g., metoclopramide, flunarizine), metabolic neurogenetic disorders (e.g., Wilson's disease), encephalitis, cerebrovascular, or degenerative disease (e.g. progressive supranuclear palsy, multiple system atrophy, vascular parkinsonism), history of pallidotomy, thalamotomy, deep brain stimulation, or fetal tissue transplant. Finally, participants will be excluded if they have any other clinically significant medical condition, psychiatric condition, drug or alcohol abuse, or laboratory abnormality which would, in the judgement of the investigator, interfere with the subject's ability to participate in the study.