This study will use a Modified Sleep Deprivation and Multiple Sleep Latency Test (MSD/MSLT) procedure. Response to the procedure will be assessed in terms of sleep continuity, sleep architecture and electroencephalographic (EEG) power spectral changes during recovery sleep. Hyperarousal will be evaluated using serial measures of somatic (cortisol) and cortical (EEG Beta/Gamma activity) arousal across the sleep deprivation protocol.