Glucose enhancement of human memory: A comprehensive research review of the glucose memory facilitation effect

Abstract

The brain relies upon glucose as its primary fuel. In recent years, a rich literature has developed from both human and animal studies indicating that increases in circulating blood glucose can facilitate cognitive functioning. This phenomenon has been termed the 'glucose memory facilitation effect'. The purpose of this review is to discuss a number of salient studies which have investigated the influence of glucose ingestion on neurocognitive performance in individuals with a) compromised neurocognitive capacity, as well as b) normally functioning individuals (with a focus on research conducted with human participants). The proposed neurocognitive mechanisms purported to underlie the modulatory effect of glucose on neurocognitive performance will also be considered. Many theories have focussed upon the hippocampus, given that this brain region is heavily implicated in learning and memory. Further, it will be suggested that glucose is a possible mechanism underlying the phenomenon that enhanced memory performance is typically observed for emotionally laden stimuli.

Hippocampal involvement in glucose facilitation of recognition memory: Event-related potential components in a dual-task paradigm

“…These findings raise the possibility that the degree of mental effort required to complete a task, rather than hippocampal involvement, is the more important determinant of task sensitivity to glucose enhancement [28]. A corollary of this theory is that glucose may facilitate memory function by targeting brain regions more globally, with effects not strictly isolated to the hippocampus [10].…”

“…A recent meta-analysis Hoyland et al [6] provided evidence to suggest that glucose may affect memory performance to a greater extent than other cognitive domains. While the exact mechanism by which glucose improves memory performance is yet to be elucidated, increased acetylcholine and insulin production and resultant effects on hippocampal function have emerged as important factors [3,[7][8][9][10][11].…”

“…Recollection is relatively more impaired in older individuals [33] and glucose impacts more in deficit populations with known hippocampal dysfunction [10,11]. One reason that glucose may be more effective in enhancing recollection in older adults is because glucose regulation becomes increasingly compromised with advancing age [2,34].…”

Memory consolidation — Mechanisms and opportunities for enhancement

“…Glucose appears to be especially important for hippocampal-dependent memory [90,91], and for demanding tasks [92][93][94]. After awakening, blood glucose levels in the brain are relatively low [88], and improvements in working memory have been demonstrated upon glucose administration -regardless of whether blood glucose levels were depleted upon time of administration [89].…”

Food for Thought: the Efficiency of Glucose Metabolism Predicts the Self-generation of Temporally Distant Cognition

“…Particularly relevant to the present investigation, a large body of research has shown that glucose metabolism is important for one of the major elements of self-generated thought; episodic memory [13,14]. Impairments in episodic memory has been observed in healthy younger individuals with poor glucose regulation [15], in middle aged adults [16] and also poor gluco-regulating adolescents after consuming a glucose containing drink [17,18,19], in older adults with and without Mild Cognitive Impairment [20] and in those individuals with impaired glucose tolerance and diabetes (see [14,21] for reviews).…”