Locus-coeruleus Function in Normal Elderly and AD Risk

Inclusion Criteria: * Male and female subjects with normal cognition and 55-75 years of age will be enrolled. * Subjects will be within normal limits on neurological and psychiatric examinations. * All subjects enrolled will have a CDR of 0. This will be evaluated through a clinical interview administered by a study physician (informant interview will not be required). * All subjects will have had a minimum of 12 years of education. Exclusion Criteria: * History of brain tumor, MRI evidence of brain damage or brain disease including significant trauma, hydrocephalus, seizures, stroke, mental retardation or other serious neurological disorder (e.g. Parkinson's disease or other movement disorders). * Significant history of alcoholism or drug abuse. * Significant history of psychiatric illness (e.g., schizophrenia, bipolar, PTSD, or life-long history of major depression). * Geriatric Depression Scale (short form)\>6. * Insulin dependent diabetes. * Evidence of clinically relevant cardiac, pulmonary, endocrine or hematological conditions. * Physical impairment of such severity as to adversely affect the validity of psychological testing. * Any prosthetic devices (e.g., pacemaker or surgical clips) that constitutes a hazard for MRI imaging. * History of a first-degree family member with early onset (age \<60 years) dementia. * Irregular sleep-wake rhythms (based on the actigraphy recordings) or significant OSA (AHI4%≥15). * Taking Coumadin/warfarin and/or medications affecting …