The study population is selected from UCLA primary care clinics, UCLA memory clinic, residents from the California counties of Orange and Los Angeles who answer ads placed in newspapers in these areas.

Inclusion Criteria:

• Agreement to participate in a clinical and brain imaging study
• Age 30 years or older
• No significant cerebrovascular disease - modified Ischemic Score of ≤ 4
• For volunteers with MCI or dementia, there must be a family member or potential caregiver available
• Adequate visual and auditory acuity to allow neuropsychological testing
• Screening laboratory tests and ECG without significant abnormalities that might interfere with the study.

Exclusion Criteria:

• Evidence of neurologic or other physical illness that could produce cognitive deterioration; in addition to a physical and neurological examination, volunteers will be screened for Parkinson's disease
• History of myocardial infarction within the previous year or unstable cardiac disease
• Uncontrolled hypertension (systolic BP>170 or diastolic BP>100), history of significant liver disease, clinically significant pulmonary disease, diabetes, or cancer
• Major psychiatric disorders, such as bipolar disorder or schizophrenia
• Because medications can affect cognitive functioning, volunteers needing medicines that could influence psychometric test results will be excluded; use of any of the following drugs will also exclude volunteers: centrally active beta-blockers, narcotics, clonidine, anti-Parkinsonian medications, benzodiazepines, systemic corticosteroids, and medications with significant cholinergic or anticholinergic effects, anti-convulsants, or warfarin
• Current diagnosis or history of alcoholism or drug dependence
• Evidence of untreated depression as determined by a HAM-D (Hamilton, 1960) score of ≥ 12 (17-item version) or untreated anxiety by a score of ≥ 8 on the Hamilton Anxiety Scale (HAM-A; Hamilton, 1959)
• Use of any investigational drugs within the previous month or longer, depending on drug half-life
• Contraindication for MRI scan (e.g., metal in body, claustrophobia)