Supplemental Tyrosine and Vigilance Performance in a Normoxic Hypobaric Environment
Abstract
Exposure to environmental or physiological stress results in a decrease in mental and physical performance. The less control the individual has over these stresses, the greater the decrement. The decrease in performance, particularly mental performance, results from a depletion of catecholamines within the brain. This decrease, especially in norepinephrine, leads to alterations in normal brain function and an increase in error rates, decreased decision making ability, mental confusion, and an overall decrease in cognitive performance. All of these are compounded the longer the individual is unable to remove the stress. Previous studies involving rats and humans have shown that supplemental tyrosine (levels above normal dietary intake) prevent the normal decrease in performance in stressed individuals. Tyrosine, the initial precursor in catecholamine synthesis, works by increasing the availability of the precursor and thereby slowing the rate of norepinephrine depletion. Nine healthy subjects from the Colorado State University community were exposed to a 3-hour protocol that was repeated for 4 different environmental conditions. During each exposure profile, the following stressors were placed on the subjects: (1) hypobaric environment of 21,000 feet (only for two of the four exposure profiles); (2) immobilization in the form of a confined space (4' x 3'), the restriction of movement for a period of three hours, and the use of a breathing hood; (3) boredom associated with periods of prolonged inactivity; (4) behavioral and psychophysiological testing; (5) cool temperatures and low humidity; and (6) a sustained 71 dB(A) noisy chamber environment. During the course of each exposure, subjects performed several computerized vigilance and cognitive tests and completed a mood questionnaire. Each test was separated by a period of inactivity. Prior to each exposure, subjects were given either 100 mg/kg body weight of a placebo or tyrosine in capsule form.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 2001
- Accession Number
- ADA392339
Entities
People
- Ryan W. Maresh
Organizations
- Air Force Institute of Technology