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Resilience and Survival in Extreme Environments 153

Mean + SEM (n=18)
−
Resistant subject
Vulnerable subject
0.0050
0.0045
0.0040
0.0035
PVT speed 0.0030
0.0025

0.0020
0.0015
0.0010
0.0005
0.0000
1 2 3 4 5 6 7 8 9 10 11 12 13
Baseline Sleep restriction Recovery
8 h/night 3 h/night 8 h/night
Figure 7.2 Psychomotor vigilance task (PVT) performance (speed) in a group
of normal subjects over 1 week of sleep restriction (center line) and two indi-
viduals representing opposite outlier responses in performance degradation.
The genomic and physiological basis of these differences is currently being
explored by researchers at the Walter Reed Army Institute of Research (WRAIR)
(Bethesda, MD). With permission, based on data provided by Tom Balkin.

decrements in cognitive function as well as mood (Killgore, Balkin &
Wesensten, 2006). Stimulant drugs may induce other behavior changes
and provide selective temporary restoration of some functions. In general,

though, most effects of sleep deprivation are magnified by ongoing wake-

fulness. For example, negative effects of sleep deprivation on judgment

are not reversed by stimulants such as high-dose caff eine, amphetamine,
or modafinil (Wesensten, Killgore & Balkin, 2005). Higher cortical func-

tions such as moral judgment are especially sensitive to sleep deprivation.
Amphetamine selectively increases risk-taking behavior without restoring
judgment, as demonstrated in one study by the willingness of sleep-deprived
soldiers to continue to march on injured feet (Cuthbertson & Know, 1947;
Tyler, 1947). Th us, artificially sustained wakefulness is risky.

Convincing data have begun to emerge from animal studies, especially
those involving fruit fl ies (Drosophila melanogaster) and mice, support-
ing the notion that genes may influence sleep patterns and responses to

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