The goal of this project is to examine the neurophysiology of hypersomnia during sleep and wakefulness, to identify biomarkers for excessive sleepiness in neuropsychiatric disorders, and pilot acoustical slow wave induction during sleep in patients with hypersomnolence, to determine if this decreases daytime sleepiness in these patients. The primary study hypotheses are that individuals with hypersomnolence will have reduced slow wave activity (SWA) during sleep and increased waking theta/alpha activity during wake in specific brain regions. A secondary hypothesis is that acoustical slow wave induction in hypersomnolent patients will increase SWA during sleep, reduce theta/alpha activity during wake, and improve subjective sleepiness.