Stress and Memory Consolidation

Abstract

This chapter presents stress modulation of learning and memory processes, focusing on the consolidation (and reconsolidation) of emotional memories in health and disease. A stressor is any kind of condition, which presents an environmental demand that exceeds the natural regulatory capacity of the individual. A stressor can be of a physical or psychological nature, tangible or mentally evoked. The subjective state of sensing these possibly adverse conditions is termed ‘stress’ and it leads to the activation of two systems: the sympathetic nervous system and the hypothalamus-pituitary-adrenal axis. Their end-products of (nor)adrenaline and glucocorticoids mediate different functions but also work in concert to promote an adaptive physiological and behavioral response to the challenge. Stress can either enhance or impair memory, and the timing of the stress relative to the task plays a major role in determining the direction of these effects. The adaptive stress response prioritizes consolidation of potentially dangerous events, therefore while consolidation is enhanced, retrieval is usually impaired. Additional factors, such as stimulus and context characteristics (e.g. emotionality and arousal), stress intensity and duration, also play a role. While in several circumstances can stress hormones lead to strong and persistent maladaptive or traumatic memories, their memory-enhancing and retrieval-impairing properties also make them potential adjuvants for treatment, e.g. in extinction-learning based therapies.