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The influence of isolation on psychological and physiological variables.

BACKGROUND
Human behavior is temporally organized by an endogenous "biological clock," and the alternation between activity and rest is an integral part of this system. Like all other biological functions, the system is only capable of adapting to external stimuli to a limited (and recognizable) extent.


HYPOTHESIS
In space, astronauts are kept in a relatively isolated and extreme environment. Under these conditions the circadian system is disturbed and specific countermeasures must be invoked in order to avoid negative consequences on sleep, mood and performance.


METHOD
The results of isolation experiments will be compared with studies in space focusing on the circadian course of variables such as body core temperature, sleep-wake patterns, mood, and performance.


RESULTS
Subjects in isolation can show disturbances of sleep, mood and vigilance if their biological rhythms run "out of phase."


CONCLUSIONS
A strict 24-h time schedule should be kept with regard to environmental, as well as behavioral influences to insure adequate and restful sleep and optimal levels of waking performance and psychological well-being.