- Research Phase I (complete testing in 10 healthy controls to assess effects on wake/sleep states on whole brain ADC) and research Phase II (complete testing in a total of 30 subjects to assess if there are regional differences) and to address the main and secondary outcomes proposed above. Only if we show that ADC significantly changes during sleep compared to awake state will we proceed to phase II. For phases I and II, the participants will spend 3 night in the clinical center and will undergo two MRI scan sessions following two fo the night stays to quantify brain ADC; once while awake (following a night of sleep) and the other while asleep (following a night of sleep deprivation). Scans for both days will be performed in the morning (between 9-12 PM). Electrocardiogram (ECG) will be recorded during all MRI scanning procedures to monitor sleep. For the first of the three nights we will simultaneously record the electroencephalogram (EEG) and ECG on the participants while they sleep which will allow us to correlate the ECG to their EEG signal, which is the gold standard for measuring sleep.