Hypobaric hypoxia (decreased oxygen supply to body tissues due to low atmospheric pressure)
caused by exposure to high altitude disrupts sleep. Sleep deprivation is associated with
degraded post-sleep performance of neurobehavioral tasks. The lowest altitude at which sleep
and/or post-sleep performance are affected is not known. The study hypothesis is that sleep
and/or post-sleep performance of neurobehavioral tasks will occur due to hypobaric hypoxia at
altitudes of 8,000 or less.