Participants playing the computer game Tetris reported intrusive, stereotypical, visual images of the game at sleep onset. Three amnesic patients with extensive bilateral medial temporal lobe damage produced similar hypnagogic reports despite being unable to recall playing the game, suggesting that such imagery may arise without important contribution from the declarative memory system. In addition, control participants reported images from previously played versions of the game, demonstrating that remote memories can influence the images from recent waking experience.
We studied time estimation in patients with frontal
damage (F) and alcoholic Korsakoff (K)
patients in order to differentiate between the contributions
of working memory and episodic memory to temporal cognition.
In Experiment 1, F and K patients estimated
time intervals between 10 and 120 s less accurately than
matched normal and alcoholic control subjects. F
patients were less accurate than K patients at
short (< 1 min) time intervals whereas K patients
increasingly underestimated durations as intervals grew
longer. F patients overestimated short intervals
in inverse proportion to their performance on the Wisconsin
Card Sorting Test. As intervals grew longer, overestimation
yielded to underestimation for F patients. Experiment
2 involved time estimation while counting at a subjective
1/s rate. F patients' subjective tempo, though
relatively rapid, did not fully explain their overestimation
of short intervals. In Experiment 3, participants produced
predetermined time intervals by depressing a mouse key.
K patients underproduced longer intervals. F
patients produced comparably to normal participants, but
were extremely variable. Findings suggest that both working
memory and episodic memory play an individual role in temporal
cognition. Turnover within a short-term working memory
buffer provides a metric for temporal decisions. The depleted
working memory that typically attends frontal dysfunction
may result in quicker turnover, and this may inflate subjective
duration. On the other hand, temporal estimation beyond
30 s requires episodic remembering, and this puts K
patients at a disadvantage. (JINS, 2000, 6,
517–528.)
Harvard Medical School Short, unfamiliar melodies were presented to young and older adults and to Alzheimer's disease (AD) patients in an implicit and an explicit memory task. The explicit task was yes-no recognition, and the implicit task was pleasantness ratings, in which memory was shown by higher ratings for old versus new melodies (the mere exposure effect). Young adults showed retention of the melodies in both tasks. Older adults showed little explicit memory but did show the mere exposure effect. The AD patients showed neither. The authors considered and rejected several artifactual reasons for this null effect in the context of the many studies that have shown implicit memory among AD patients. As the previous studies have almost always used the visual modality for presentation, they speculate that auditory presentation, especially of nonverbal material, may be compromised in AD because of neural degeneration in auditory areas in the temporal lobes.
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