Regional Rates of Cerebral Protein Synthesis: Effects of Sleep and Memory Consolidation

Background: * The brain needs sleep to function normally, but the purpose of sleep is not understood. Brain activity decreases during sleep, so it may be that sleep is important to maintain, repair, or reorganize brain cells. In animals, the formation of brain proteins increases during sleep, and the same thing may happen in humans. * There is also evidence that learning and memory are helped by sleep, and that the synthesis of proteins in the brain are involved. Objectives: * To examine the formation of proteins in the brain while people are awake, deprived of sleep, and during sleep. * To look at the formation of proteins in the brain while awake or asleep and following learning a task. Eligibility: * Healthy volunteers between 18 and 28 years of age. * Volunteers must not have psychiatric, neurologic, or sleep disorders or certain types of vision problems, and must be able to undergo imaging studies. Design: * Study Part I (protein formation in waking, sleep deprivation, and sleep): * Participants will wear an actigraph (a unit to record motor activity) for 2 weeks prior to admission. * Participants will have physical and psychological examinations, along with a blood sample. * After admission participants will have three positron emission tomography (PET) scans to study protein formation and one magnetic resonance imaging (MRI) scan over the course of two days. * Participants may be asked to stay awake for as long as 20 hours and will be monitored throughout. * Participants will be able to sleep overnight after they complete the required scans and monitoring, and will be discharged the following morning. * Study Part II (protein formation in waking and sleep combined with a learning task): * Participants will wear an actigraph (a unit to record motor activity) for 2 weeks prior to admission. * Participants will have physical and psychological examinations, along with a blood sample. * After admission participants may be asked to stay awake for as long as