The influence of glucose administration on stress reactivity and long-term memory in adult men and women

Stress and the associated cortisol release have profound effects on long-term memory (LTM). While glucose increases the cortisol stress response and exhibits memory enhancing effects in non-stressful situations, the interaction of glucose and stress on LTM has rarely been studied. The aim of this study was to investigate whether the glucose-related amplification of the cortisol stress response would enhance LTM formation. Overall, N = 62 healthy, fasted adults (age M = 23.13, SD = 3.02; 54.84 % female) participated. They consumed a drink containing water or glucose and underwent a non-stressful control task or the Trier Social Stress Test with Objects, during which panel members interact with certain objects (central) while leaving others untouched (peripheral). At the estimated cortisol peak, they encoded a wordlist. On the next day, they retrieved the objects and the words. We repeatedly assessed subjective stress, salivary cortisol and blood glucose concentrations and recorded an electrocardiogram. Glucose increased blood glucose concentrations, and the stressor led to a significant increase in cortisol as compared with the control task. Changes in cortisol were more pronounced in the glucose as compared with the water groups. Heart rate was elevated in the glucose as compared with the water groups during the recovery. Central objects were better remembered than peripheral objects when encoded during stress. Additionally, emotional words were remembered better as compared with neutral words. These effects were not modulated by glucose. These findings suggest that emotional information is remembered better than neutral information independent of stress and glucose intake. Stress enhances LTM of stressor-relevant information and glucose intake increases the cortisol stress response. However, these factors do not appear to interact. Glucose availability may thus play a less decisive role when memorizing a stressful episode.