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Abstract:
The complex and bizarre imagery seen in dreaming may reflect
cognitive processes altered during sleep-dependent memory
consolidation and integration. Similarly, intrusive pre-sleep
thoughts and images may reflect an early onset of this nocturnal
memory reprocessing. To investigate this phenomenon, 12 subjects
with no experience playing the computer game Tetris played 8 hr of
Tetris over 4 days; 2 hr at the first exposure and 1 hr each
subsequent morning and evening. During the first two nights,
subjects were automatically and repetitively prompted for mentation
reports during the first hour of attempted sleep. Data from 10
subjects have been analyzed. Subjects averaged 7.7 reports per
night, for a total of 154 reports over two nights. Of these, 15
(10%) contained specific references to visual images of Tetris
pieces, and 23 (15%) reported thinking about Tetris. While reports
of thoughts were distributed evenly between the two nights (10 on
Night 1, 13 on Night 2; chi-square = 0.02, p = 0.90), the
distribution of intrusive images was not (chi-square = 10.7, p =
0.001), with 14 of the 15 reports occurring on Night Two. Thus,
there is normally a minimum of a 24-hr delay before such imagery
appears at sleep onset. More detailed analyses suggest that these
automatic, intrusive images reflect the onset of a delayed
reprocessing of highly repetitive, emotionally salient, visual
images.
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