Glucose effects on long-term memory performance : duration and domain specificity.

Rational; Previous research has suggested that long term- verbal declarative memory is particularly sensitive to enhancement by glucose loading, however investigation of glucose effects on certain memory domains has hitherto been neglected. Therefore domain specificity of glucose effects merits further elucidation. Objectives; The aim of the present research was to provide a more comprehensive investigation of the possible effects of glucose administration on different aspects of memory by i) contrasting the effect of glucose administration on different memory domains (implicit/ explicit memory; verbal/ non-verbal memory, recognition/ familiarity processes), ii) investigating whether potential effects on memory domains differ depending on the dose of glucose administered (25g versus 60g), iii) exploring the duration of the glucose facilitation effect (assessment of memory performance 35 min and 1 week after encoding). Methods; a double blind, between- subjects design was used to test the effects of administration of 25 and 60g glucose on memory performance. Results; Implicit memory was improved following administration of 60g of glucose. Glucose supplementation failed to improve face recognition performance but significantly improved performance of word recall and recognition following administration of 60g of glucose. However, effects were not maintained one-week following encoding. Conclusions; Improved implicit memory performance following glucose administration has not been reported before. Furthermore the current data tentatively suggest that level of processing may determine the required glucose dosage to demonstrate memory improvement and that higher dosages may be able to exert effects on memory pertaining to both hippocampal and non-hippocampal brain regions