Orexin and Tau Pathology in Cognitively Normal Elderly

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 both a Clinical Dementia Rating (CDR)=0 and a MMSE≥27 * All subjects will have had a minimum of 12 years of education. Among minority subjects \>80% of the elderly individuals coming to the NYU-ADC meet this criterion. (The education restriction reduces performance variance on cognitive test measures and improves the sensitivity for detecting pathology and disease progression using the robust norms available at NYU. Given the majority of subjects will meet this criterion we do not consider this a major selection bias or generalization limitation for this study). * An informed family member or life-partner (preferably bed-partner) will be interviewed over the phone or on the first or second visit to confirm the reliability of the subject interview. Exclusion Criteria: * History of brain tumor, MRI evidence of brain damage or brain disease including significant trauma, hydrocephalus, seizures, mental retardation or other serious neurological disorder (e.g. Parkinson's disease or other movement disorders). Subjects with a Fazekas scale \>2 will be excluded109. * Significant history of alcoholism or drug abuse. * History of psychiatric illness (e.g., schizophrenia, bipolar, PTSD, or life-long history of major depression). * Geriatric Depression Scale (short form)\>5. * Insulin dependent diabetes. * Evidence of clinically relevant cardiac, pulmonary, endocrine or hematological conditions (e.g. low platelet levels). * 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 or CBT measurements. * 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). * Medications affecting cognition or sleep. * Presence of any known or suspected obstructive disease of the gastrointestinal tract, including but not limited to diverticulitis and inflammatory bowel disease. * History of disorders or impairment of the gag reflex. * Previous gastrointestinal surgery. * Previous felinization of the esophagus. * Subjects who might undergo Nuclear Magnetic Resonance (NMR) or MRI scanning during the period that the CorTemp® Disposable Temperature Sensor is within the body. * Subjects hypomotility disorders of the gastrointestinal tract including but not limited to Ileus.