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Abstract:
Twelve experimental participants were monitored
polysomnographically for four nights, including normal sleep, REM
sleep fragmentation, and slow-wave sleep (SWS) fragmentation,
counterbalanced across subjects. On fragmentation nights, subjects
heard a loud tone at short intervals in either REM or SWS, which
would not stop until the subject sat up. This manipulation caused
about a 50% decrease in the sleep stage being fragmented, as well
as a reliable decrease in bout duration, but did not reduce total
sleep time for the night. It was more difficult to fragment REM
than SWS, requiring significantly more tones during the night. In
the morning, subjects were quite accurate at recalling the number
of tones played during REM but not SWS. Subjects studied verbal and
spatial stimuli before bed and were tested on these in the morning.
Results suggest that shortened SWS bout duration is associated with
decreased recognition hit rate for verbal stimuli, while longer SWS
bout duration is associated with benefits for spatial memory. A
waking control group studied the same materials as the experimental
group in the morning and returned approximately 8 hours later the
same day to be tested. Interestingly, subjects who got either
normal or fragmented sleep had significantly reduced false alarm
rates relative to awake controls, although their hit rates were not
different. Explanations involving criterion shifts and reduced
interference will be explored.
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