The sympathetic nervous system and HPA axis interact to influence memory: the experimental understanding

Stressful or emotionally arousing experiences are typically well remembered. In my presentation I will describe findings from animals experiments indicating that sympathetic activation and peripheral catecholamines, epinephrine and norepinephrine, as well as hypothalamo-pituitary-adrenal activation enhance the consolidation of memory during stressful or emotionally arousing experiences. In contrast, catecholamines and glucocorticoid hormones impair the retrieval of memory processing. These stress hormones do not uniformly modulate memory of all kinds of information but, rather, preferentially influence the consolidation and retrieval of memory of emotionally arousing information or during emotioally arousing test situations. These findings fit well with extensive evidence from our laboratory indicating that emotional arousal-induced noradrenergic activation within the basolateral complex of the amygdala (BLA) is critically involved in mediating such stress hormone effects on memory consolidation and memory retrieval. Evidence that lesions of the BLA or infusions of a beta-adrenoceptor antagonist into the BLA block the modulatory effects of stress hormone administration on memory suggests that arousal-induced noradrenergic activation within the BLA is a co-requirement in enabling stress hormone effects to modulate memory consolidation.