Glucose enhances newborn memory for spoken words

Fuel for Thought? A Systematic Review of Neuroimaging Studies into Glucose Enhancement of Cognitive Performance

A transient improvement in cognitive performance can be observed following the ingestion of a glucose drink, a phenomenon known as the ‘glucose facilitation effect’. The effect has been studied thoroughly in the last three decades, but its neural underpinnings remain a matter of speculation. A systematic review was conducted to evaluate the current evidence from studies applying neuroimaging or neurophysiological methods to investigate the glucose enhancement effect. Eleven studies met the inclusion criteria of using neuroimaging in conjunction with cognitive outcomes. Six studies employed electroencephalography (EEG), four used functional magnetic resonance imaging (fMRI) and one employed functional near-infrared spectroscopy (fNIRS). All but one study reported modulation of neurophysiology or neuroimaging markers following glucose, while only five studies reported significant changes in cognitive outcomes. The evidence suggests that glucose administration enhances neurocognitive markers of episodic memory and attentional processes underpinned by medial temporal and frontal activation, sometimes in the absence of measurable behavioural effects. Further exploration of glucose facilitation using neuroimaging measures with increased sample sizes is warranted to replicate these findings.

Verbal positional memory in 7-month-olds

Verbal memory is a fundamental prerequisite for language learning. This study investigated 7-month-olds' (N = 62) ability to remember the identity and order of elements in a multisyllabic word. The results indicate that infants detect changes in the order of edge syllables, or the identity of the middle syllables, but fail to encode the order of middle syllables. This suggests that the representational format of multisyllabic words is determined by core mnemonic biases, which favor accurate encoding of edges and limits the encoding of temporal order for internal segments. The studies support accounts proposing that content and order are encoded separately; in addition, the data show that this dissociation occurs early in development.

The role and requirements of digestible dietary carbohydrates in infants and toddlers

Digestible carbohydrates are one of the main sources of dietary energy in infancy and childhood and are essential for growth and development. The aim of this narrative review is to outline the intakes of digestible carbohydrates and their role in health and disease, including the development of food preferences, as well the consequences of excess carbohydrate. Key experts in these fields provided up-to-date reviews of the literature. A search of available information on dietary intakes of children below the age of 4 years was conducted from 1985 up to 2010. Articles and reports including information about sugars and/or starch intakes were selected. A number of factors limit the ability to obtain an overall picture of carbohydrate intakes and food sources in this age group. These include small numbers of intake studies, differing approaches to analysing carbohydrate, a variety of terms used to describe sugars intakes and a dearth of information about starch intakes. Data suggest that sweet taste is preferred in infancy and later food choices. There are few established adverse consequences of high intakes of digestible carbohydrate for young children. The greatest evidence is for dental caries, although this is influenced by high intake frequency and poor oral hygiene. Evidence for detrimental effects on nutrient dilution, obesity, diabetes or cognition is limited. In infants, minimum carbohydrate (mainly lactose) intake should be 40% of total energy, gradually increasing to 55% energy by the age of 2 years.

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

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.

Glucose modulates event-related potential components of recollection and familiarity in healthy adolescents

INTRODUCTION

Behavioural evidence supports the notion that oral glucose ingestion enhances recognition memory judgements based on recollection, but not familiarity. The present study sought to clarify and extend upon these behavioural findings by investigating the influence of glucose administration on event-related potential (ERP) components that are thought to be differentially mediated by recollection and familiarity processes in healthy adolescents.

METHODS

In a within-subjects design, participants performed a recognition memory task, during which time electroencephalogram (EEG) was recorded, subsequent to ingestion of either (a) glucose or (b) placebo in a counterbalanced order.

RESULTS

Response times during the recognition memory task were observed to be faster for the glucose condition, relative to a placebo control. Further, glucose ingestion was associated with an enhanced left parietal old/new ERP effect (a marker of recollection) and an enhanced mid-frontal old/new ERP effect (known to be mediated by familiarity).

DISCUSSION

These findings (a) support the results of previous research that the 'glucose memory facilitation effect' can be extended to healthy adolescents, but (b) suggest that glucose enhances both the recollection and familiarity components of recognition memory. The observed ERP profile has important implications for the proposal that glucose specifically targets the hippocampus in modulating cognitive performance.

Glucoregulatory and order effects on verbal episodic memory in healthy adolescents after oral glucose administration

The ingestion of oral glucose has been observed to facilitate memory performance in both elderly individuals and in young adults. However, fewer studies have investigated the effect of glucose on memory in children or adolescents. In the present study, the ingestion of a glucose laden drink was observed to enhance verbal episodic memory performance in healthy adolescents under conditions of divided attention, relative to a placebo drink. Further analyses found that this glucose memory facilitation effect was observed only in adolescents exhibiting better glucoregulatory efficiency. These findings demonstrate that the glucose memory facilitation effect can be generalised to younger individuals. The importance of controlling for treatment order in within-subjects designs investigating the glucose memory enhancement effect is also discussed.