An MSLT is a daytime study, which follows your overnight diagnostic sleep study, to test for narcolepsy. In the morning, some of the leads and belts are removed. During the MSLT, you will have a series of five 20-minute napping periods throughout the day. During breaks between napping, we will ask that you stay awake. Your physician is interested in three things: if you go to sleep at every napping opportunity, how quickly you go to sleep, and if you go into deep, restorative, rapid-eye-movement (REM) sleep.