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Abstract:
Increasing peripheral availability of glucose has previously
been shown to enhance some memory performance, presumably due to a
related increase in central glucose utility. The possible link
between glucose-induced memory enhancement and task difficulty was
investigated using human participants. In Experiment 1,
participants were required to learn 16 paired associates (8 high
imagery, 8 low imagery). They learned the pairs to a predefined
criterion level and were tested at three retention intervals; 24
hrs, 1 week, and 2 weeks after learning. Consumption of glucose
enhanced retention for low but not high imagery pairs. In
Experiment 2 we incorporated an additional two variables: age and
glucose regulation. We hypothesised that glucose ingestion would
improve memory performance, and that this improvement would be
linked to participants' ability to regulate glucose. We observed a
glucose-induced enhancement for word list recall. Good glucose
regulation was related to good memory performance in older adults,
but was not found to be a significant factor in young adults. In a
memory search task, we found that for older adults, glucose-induced
facilitation was greatest in conditions of high cognitive demand.
The results support the suggestion that such memory enhancement may
be linked to task difficulty, and that more difficult tasks produce
greater glucose facilitation. We suggest a link with hippocampal
acetylcholine, as well as a potential link between cholinergic
activation and task difficulty.
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