Investigation into the significance of task difficulty and divided allocation of resources on the glucose memory...

Memory for a list of 20 words can be enhanced by preceding learning with consumption of 25 g glucose rather than an equally sweet aspartame solution. In previous studies, participants performed a secondary hand-movement task during the list-learning phase.

The present placebo-controlled, double-blind study examined whether the additional cognitive load created by a secondary task is a crucial feature of the glucose memory facilitation effect.

The effect of glucose administration on word recall performance in healthy young participants was examined under conditions where the primary memory task and a secondary task were competing for cognitive resources (across a range of secondary tasks), and where task difficulty was increased but dual task-mediated competition for cognitive resources did not exist. Measures of non-verbal and working memory performance were also compared under the different glycaemic conditions (glucose versus aspartame drinks).

In the present study, a beneficial effect of glucose on memory was detected after participants encoded a 20-word list while performing a secondary task, but not when participants encoded the list without a secondary task, nor when the 20 target words were intermixed with 20 non-target words (distinguished by gender of speaker). In addition, glucose significantly enhanced performance on spatial and working memory tasks.

The data indicate that possible "depletion" of episodic memory capacity and/or glucose-mediated resources in the brain due to performing a concomitant cognitive task might be crucial to the demonstration of a glucose facilitation effect. Possible implications regarding underlying cognitive and physiological mechanisms are discussed in this article.