This proposed laboratory study will extend previous findings on relationships between cognitive function and nutritional status to conditions that more closely resemble military operations where aerobic exercise, inadequate nutritional intake and sleep deprivation combine to degrade cognitive function. The investigators will examine cognitive function, brain activity and glucose levels in volunteers who are calorie-deprived, performing high workload cognitive tests, exercising and, in one arm of the study, are sleep-deprived for approximately 48 hours. A comprehensive cognitive test battery will be repeatedly administered and several cognitive tests will be administered when volunteers are exercising. Interstitial glucose levels will be assessed and whole body nitrogen utilization determined. The effects of energy restriction and the physiological basis of the relationship between peripheral glucose levels and cognitive function will be examined using a state-of-the-art imaging technology, functional Magnetic Resonance Imaging (fMRI). This technique will allow any key brain regions affected by caloric deprivation to be identified.

Inclusion Criteria:

• MUST BE ACTIVE DUTY ARMY STATIONED AT NATICK SOLDIER SYSTEMS CENTER
• Fluent in English (non-native English speakers can be enrolled); males and females aged 18 - 39 years.

Exclusion Criteria:

• Not yet reached 18th birthday, metal implants - which can interfere with fMRI scanning; fear of small places; pregnant (USARIEM will test for pregnancy), Attention Deficit Hyperactivity Disorder (ADHD) - if previously documented by a waiver; acute or chronic physical limitation that would hinder performing cycle exercise; known allergies to medical adhesives.