In recent years, there has been increased focus on cognitive side effects of sleep-inducing medications that may contribute to unusual behavior during unexpected awakenings during the night. Concerns regarding these side effects have led to a class Food and Drug Administration (FDA) warning for all sleep-inducing medications. Almorexant is an experimental sleep-inducing medication in a new class of medications that is being extensively developed by multiple pharmaceutical companies. Medications in this class block wake/arousal centers in the brain that function with proteins called hypocretins. The goal of this study is to evaluate the impact on cognitive performance of almorexant vs. zolpidem (an approved sleep aid) or placebo.

Up to 216 healthy volunteers will be enrolled to participate in the 10 day study. After screening procedures have been completed (at SFVAMC), Days 1 - 7 will take place in subjects' homes, where their sleep/wake activity will be monitored. Days 8 - 10 will take place at Moffitt Hospital. On Day 10, subjects will take one dose of either almorexant 100mg, almorexant 200mg, zolpidem 10mg, or placebo. Cognitive tests will be administered to subjects throughout Day 10. Subjects will return for follow-up safety labs within 5 - 12 days of dosing with study medication. Based on animal studies, it is anticipated that subjects who take almorexant will be less cognitively impaired than those who take zolpidem.

To participate in the study, participants must:

• Be between the ages of 19 and 39
• Be in good physical health
• Be a good sleeper with consistent bedtimes and wake times
• Not have problems falling or staying asleep
• Be a non-smoker
• Meet our other study criteria