Slowing effects of glucose-rich drinks on response speed. An electrophysiological study using the Flanker task

Abstract

Modulations of blood glucose levels affect brain function. These effects are well described for hypoglycaemia, however much less is known about how variations of blood glucose levels within the normal range affect cognition, information processing and behaviour. A small body of empirical evidence suggests that elevated glucose levels, induced by glucose-rich drinks, can boost cognitive performance. However, other studies have failed to find such effects. Anecdotal reports by teachers and parents further imply that glucose consumption can impair behaviour and cognition. The present study therefore aimed to further explore the interaction of elevated blood glucose levels with behaviour. In a double-blind placebo controlled experiment with a glucose and placebo group, we show that glucose-enriched drinks slow reaction times during the learning of stimulus-response associations in the Eriksen Flanker Task. The electrophysiological data further indicated reduced event-related-potentials as well as a delayed stimulus-locked lateralised readiness potential, an indicator of response selection, in the glucose group. These data suggest that elevated glucose levels can impair sensorimotor processing. Physiologically, these effects might be mediated by a slowing of neural conduction velocity arising from the oxidative stress glucose metabolism exerts on Na+ channels.