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 can increase 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 the current study was to investigate whether the glucose related amplification of the cortisol stress response would further enhance LTM formation. Overall, N = 62 healthy adults (age M = 23.13, SD = 3.02; 54.84 % female) participated after a 5 h fast. Participants consumed a drink containing glucose or water and subsequently underwent the Trier Social Stress Test with Objects or a non-stressful control task. At the estimated cortisol peak, they encoded a word list. On the next day, they memorized the objects and the word list. We repeatedly assessed salivary cortisol, blood glucose concentrations and subjective stress. 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 group. Central objects were better remembered than peripheral objects when encoded during stress, but glucose did not enhance this effect. Additionally, emotional words were remembered better as compared with neutral words. 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.