Neurophysiologic Correlates of Hypersomnia

Brief tones (50 millisecond duration) at a frequency of 0.8 and 2 Hz, a rate that approximates the natural cellular oscillations of cortical neurons during sleep, will be played in blocks of 15-20 during non-rapid eye movement (NREM) sleep. Blocks of active acoustic slow wave induction will be followed by blocks of equal duration without induction, in order to make comparisons between stimulation periods (ON) and no stimulation periods (OFF). Tone intensity will be manually adjusted so as to be above an individual participant's auditory threshold during waking, but still quiet enough as not to awaken the subject from sleep. Sham slow wave induction will consist of auditory tones played prior to sleep, and during sleep of insufficient timing and intensity to alter slow wave activity.