2-deoxyglucose induces LTP in layer I of rat somatosensory cortex in vitro

Prolonged rote learning produces delayed memory facilitation and metabolic changes in the hippocampus of the ageing human brain

BACKGROUND

Repeated rehearsal is one method by which verbal material may be transferred from short- to long-term memory. We hypothesised that extended engagement of memory structures through prolonged rehearsal would result in enhanced efficacy of recall and also of brain structures implicated in new learning. Twenty-four normal participants aged 55-70 (mean = 60.1) engaged in six weeks of rote learning, during which they learned 500 words per week every week (prose, poetry etc.). An extensive battery of memory tests was administered on three occasions, each six weeks apart. In addition, proton magnetic resonance spectroscopy (1H-MRS) was used to measure metabolite levels in seven voxels of interest (VOIs) (including hippocampus) before and after learning.

RESULTS

Results indicate a facilitation of new learning that was evident six weeks after rote learning ceased. This facilitation occurred for verbal/episodic material only, and was mirrored by a metabolic change in left posterior hippocampus, specifically an increase in NAA/(Cr+Cho) ratio.

CONCLUSION

Results suggest that repeated activation of memory structures facilitates anamnesis and may promote neuronal plasticity in the ageing brain, and that compliance is a key factor in such facilitation as the effect was confined to those who engaged fully with the training.

Unlike 2-deoxy-D-glucose, 3-O-methyl-D-glucose does not induce long-term potentiation in rat hippocampal slices

Equimolar replacement of 10 mM glucose by 2-deoxy-D-glucose (2-DG) causes substantial depression followed by a sharp and sustained potentiation of CA1 field EPSPs. In the present experiments, similar applications of 3-O-methyl-D-glucose, which is also taken up by cells but is not phosphorylated, had only a weak blocking action and elicited no potentiation. Possible explanations for the marked effects of 2-DG include a more rapid block of glycolysis and the production of phosphorylated derivatives of 2-DG.