Inclusion Criteria:

• Diagnosis of one of the syndromes of interest using established criteria
• Age 40-90 inclusive
• MMSE score above 10
• No active medical disorder that could preclude participation
• Stable medication regimen over previous four weeks
• Absence of certain medications that could significantly impact the DaTscan findings
• For those with dementia, caregiver that is with the patient at least 4 hours/day for at least 5 days per week
• For those with dementia, or severe parkinsonism, patient and caregiver willing and able to participate in all study-related procedures
• Patient is capable of giving informed consent, or if appropriate, has caregiver capable of giving consent on the subject's behalf.

Exclusion Criteria:

• Does not fulfill criteria for any of the desired diagnoses
• Age <40 or >90
• Women with intact uterus and not post-menopausal unless pregnancy test performed at screening is negative
• Women who are pregnant or are breast-feeding an infant
• MMSE score <10
• Active medical disorder that could preclude participation in this protocol
  • Hypersensitivity to the radioligand, cocaine, or iodine (including seafood allergy)
  • Myocardial infarction or cerebral infarct over preceding year, stable or unstable angina, known symptomatic coronary artery disease
  • Renal or liver disease viewed by the physician to be too severe to warrant DaTscan infusion/imaging
  • History of significant alcohol or drug abuse
  • Any other medical disorder considered by the study physicians as inappropriate for this protocol
• Patient or caregiver unwilling or unable to participate in all study-related procedures
• Caregiver is not with a patient with dementia or severe parkinsonism at least 4 hours/day for at least 5 days/week
• Patient or caregiver unwilling or unable to provide informed consent