The purpose of this study is to determine if brief sounds or tones presented within a restricted period of recovery sleep after a period of sleep deprivation will enhance restorative properties and improve performance during a subsequent period of wakefulness.

Inclusion Criteria:

• Healthy men and non-pregnant, non-lactating women 18 to 39 years of age (inclusive)
• Must demonstrate adequate comprehension of the protocol, by achieving a score of at least 80% correct on a short multiple-choice quiz. Individuals who fail to achieve a passing score on the initial quiz will be given one opportunity to retest after a review of protocol information. Individuals who fail the comprehension assessment for the second time will be disqualified.

Exclusion Criteria:

• You must have learned English as your first language
• You must have a body mass index (BMI) below 30 (this is a mathematical calculation of your height and weight)
• You must not have current or a history of sleeping problems (for example, insomnia or sleep apnea), or symptoms that indicate a potential sleep disorder
• You must get an average of 6-9 hours of sleep per night and maintain a normal sleep/wake schedule
• You must not drink excessive amounts of caffeine, alcohol, or smoke cigarettes regularly
• You must not be on certain medications (determined on a case by case basis)
• You must test negative for illicit drugs
• Women must not be pregnant or nursing
• You must not be participating in another ongoing clinical trial
• You must have a social security number or tax identification number in order to be paid for screening and participation in the study
• You cannot have a history of the following conditions: Cardiovascular disease, a neurologic disorder, pulmonary disease requiring inhaler use, kidney disease or kidney abnormalities, liver disease of liver abnormalities, a history of psychiatric disorder requiring hospitalization or medication within the last two years or for a continuous period of more than 6 months in the last ten years