Moderate hypoglycaemia after learning does not affect memory consolidation and brain activation during recognition in non-diabetic adults.

Full Abstract

INTRODUCTION: Some aspects of memory performance are impaired during acute hypoglycaemia. The hippocampus is critical to formation of long-term memory, and may be particularly sensitive to hypoglycaemia. This study examined whether moderate hypoglycaemia occurring after learning would disrupt the consolidation process, and used functional magnetic resonance imaging (fMRI) to identify accompanying changes in brain activation. METHODS: Sixteen non-diabetic subjects each underwent two glucose clamp studies. During euglycaemia (4.5 mmol/L), subjects tried to memorize a series of words and a series of pictures of faces. Then, either hypoglycaemia (2.5 mmol/L) was induced for one hour, or euglycaemia was maintained. During subsequent uncontrolled euglycaemia, subjects' recognition of the word and face stimuli was tested, with simultaneous fMRI to measure brain activation during recognition. RESULTS: Face identification scores were 67.2% after euglycaemia and 66.9% after hypoglycaemia (p = 0.895). Word identification scores were 78.0 and 77.1% respectively (p = 0.701). Analysis of the fMRI identified two foci where activation was altered after hypoglycaemia compared with euglycaemia, but these were not in regions associated with memory, and were probably statistical artefacts. CONCLUSIONS: One hour of hypoglycaemia at 2.5 mmol/L induced 20-40 min after learning did not disrupt memory consolidation. fMRI did not show evidence of altered brain activation after hypoglycaemia. Consolidation may be relatively resistant to hypoglycaemia, or may have been complete before hypoglycaemia was induced. The study was powered to detect a large effect, and provides some reassurance that moderate hypoglycaemia does not cause major disruption of previously learned memories in people with insulin-treated diabetes. Copyright (c) 2008 John Wiley & Sons, Ltd.

Author information

Author/s: Warren, Roderick E (RE); Sommerfield, Andrew J (AJ); Greve, Andrea (A); Allen, Kate V (KV); Deary, Ian J (IJ); Frier, Brian M (BM);

Affiliation: Department of Diabetes, Royal Infirmary of Edinburgh, UK.

Journal and publication information

Publication Type: Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.

Journal: Diabetes/metabolism research and reviews (Diabetes Metab Res Rev), published in England. (Language: eng)

Reference: -2008 Mar-Apr; vol 24 (issue 3) : pp 247-52

Dates: Created 2008/03/03; Completed 2008/06/03;

PMID: 18088081, status: MEDLINE (last retrieval date: 2/18/2009, IMS Date: )

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