Abstract
Orientation and self-location within the temporal fabric of the environment
involves multiple organismic systems. While temporal self-location
on the physiological level has been known for some time to be based
on a ‘biological clock’ located within the hypothalamus, the mechanisms
that participate in temporal position finding on the cognitive level
are not yet fully understood. In order to probe the mechanisms that
underlie this faculty, verbal estimates on time-of-day were collected
at 3.75-h intervals from 16 young (7 males, 8 females; 20–31 years)
and 16 older (8 males, 8 females; 57–74 years) subjects in a balanced
crossover design during 40-h epochs of prolonged wakefulness and
40-h epochs of sleep satiation spent under constant routine conditions.
An overestimation of clock time during prolonged wakefulness was
found in both age-groups, with significantly larger errors for the
older group (young: h; older: h, p < 0.05). In both age-groups,
estimation errors ran roughly parallel to the time course of core
body temperature. However a significant interaction between time-of-day
and age-group was observed (rANOVA, p < 0.05): younger subjects exhibited
similar estimation errors as the older subjects after 16 h of prior
wakefulness, whereas the latter did not manifest decrements under
high sleep pressure. Data collected under conditions of sleep satiation
also displayed a diurnal oscillation in estimation errors and a general
overestimation (young: h; older: h, p < 0.05). Here however, the
age-groups did not differ significantly nor was there an interactive
effect between time-of-day and age-group. The effects of age, duration
of wake time and circadian phase on temporal position finding are
in line with predictions based on the idea that awareness about current
position in time is derived from interval timing processes.
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