 Design. The study is designed to facilitate MRI detection of cerebral metabolic differences between the sleep and awake states. Wakefulness and sleep, and the various stages will be classified in accordance with the EEG criteria, consistent with the guidelines of Rechtschaffen and Kales Rechtschaffen, 1968. For this purpose, we will optimize the methodology for the concurrent acquisition of EEG and fMRI signals. Using concurrent EEG and state-of-the-art MRI, we plan to establish the precise spatial distribution of changes in brain activity that are associated with changes in the sleepwake state and the various stages of sleep, specifically early sleep stage 1 and 2. Secondly, we plan to investigate whether changes in regional brain metabolism as measured by MRI correlates with transitory EEG phenomena during sleep, including fluctuations in band-specific power, sleep spindles, and K-complexes. 