The primary objectives of the proposed experimental and modeling efforts are to quantify the influences of acute sleep deprivation (short-term homeostatic), chronic sleep restriction (long-term homeostatic), circadian rhythmicity, and their interactions on neurocognitive performance and to develop a new model of sleep homeostasis that can predict the effects of chronic sleep restriction. This model will be based on the underlying neuroanatomy and neurophysiology. This new model will facilitate optimization of human performance in operational settings, such as are seen in military operation and other work environments.

This protocol involves a baseline period consisting of 14 hours of wakefulness and 10 hour nocturnal sleep episodes each 24 hours. This is followed by a forced desynchrony regimen spanning 21 calendar days and consisting of 12 cycles ("days") of a 42.85-hour wake:bedrest schedule. In each 42.85 hour cycle, there are 32.85 hours of scheduled wakefulness and 10 hour sleep opportunities. This will allow assessment of the independent contributions of circadian phase and homeostatic sleep pressure on sleep and neurobehavioral performance. This forced desynchrony regimen is followed by 10 recovery days consisting of 14 hours of wakefulness and 10 hour nocturnal sleep episodes each 24 hours.

Inclusion Criteria:

• Age 18-35 years old
• Medically healthy

Exclusion Criteria:

• Sleep disorder
• Psychiatric illness
• Chronic medical condition
• No prescription or Non-prescription medications