Eligibility

• Inclusion criteria: Subjects must be between the ages of 45-95, have a neurodegenerative disorder or be a healthy, age-matched normal control, have a Mini Mental State Examination (MMSE) score of 20 or greater and a Geriatric Depression Scale (GDS) score less than 20.
• Exclusion criteria: Previous history of Korsakoff encephalopathy, alcohol abuse or dependence within 5 years of onset of dementia, substance abuse, head trauma with loss of consciousness greater than 30 minutes, brain tumor, multiple sclerosis, epilepsy, hydrocephalus, schizophrenia, bipolar affective disorder, intracerebral hemorrhage, current history of pacemaker, ferromagnetic material in soft tissue, B12 deficiency, hypothyroidism (TSH>150% of normal), known HIV, renal failure, respiratory failure requiring oxygen, history of major depression within the past 2 years, Geriatric Depression Scale (GDS) score greater than 20, anxiety disorder due to other than dementia and requiring medication more than 3x per week, cerebral infarct, large confluent white matter lesions or grade 4 white matter lesions as described by Schletens et al., significant systematic medical illnesses such as deteriorating cardiovascular disease, clinically relevant EKG changes, current medication likely to affect central nervous system (CNS) functions.