Propofol's Hypnotic and Memory Effects

Inclusion Criteria: * Healthy normal volunteers who show no evidence of neurologic deficit on questionnaire and physical examination * Females of child-bearing age must be non-pregnant as demonstrated using a pregnancy test, non-lactating, and must be using adequate contraception or be surgically sterile * Age 18 years to 45 years * Right hand dominant * High school education or above(to ensure consistent performance on the memory tests being administered) * English as native language or equivalent degree of fluency Exclusion Criteria: * Any evidence of neurologic deficit including seizures, history of severe head trauma or any previously or current abnormal study of CNS - (eg. MRI, EEG, etc.) * Any deficit in auditory or visual ability that would prevent performance of the study tasks * History of claustrophobia * Any history of hypertension (resting BP \>150 systolic, \>100 diastolic) or taking anti- hypertensive medication * Any history of cardiovascular disease including previous myocardial infarction, arrhythmia, heart valve disease, or cardiac murmur * Significant pulmonary, renal, gastrointestinal, or endocrine metabolic disease which in the opinion of the investigator would complicate the goals of this study * Allergy to propofol, thiopental, eggs or history of acute intermittent porphyria, history of severe allergic reaction (e.g. anaphylactic shock) * History of substance abuse * Currently taking centrally acting medications (benzodiazepines or other anxiolytics, antidepressants, antipsychotic agents, or agents affecting the cerebral vasculature) * Any one who is not NPO for at least 6 hours * Any implant incompatible with MR scanning * Anyone who, in the opinion of the investigators, would be unwilling or unable to tolerate the procedures and/or comply with the task instructions * Body Mass Index (BMI) \> 30