Post-learning Stress Facilitates Long-term Memory Consolidation
Stress-induced alterations of learning and memory underlie the formation of traumatic memories and, thus, one of the most debilitating and costly psychological disorders that society faces, post-traumatic stress disorder (PTSD). However, the effects of stress on learning and memory are complex and still poorly understood. One relatively consistent finding in this area has been that post-learning stress enhances long-term memory; however, recent work has challenged this view with contradictory findings. Therefore, we examined the influence of post-learning stress on 24-hr declarative memory. Fifty-two participants learned a list of words varying in emotional valence and arousal and were then given an immediate free recall test. Participants then submerged their dominant hand in a bath of ice cold (stress) or warm (no stress) water for 3 min. Twenty-four hours later, participants returned to the laboratory and completed free recall and recognition assessments. Results indicated that stress enhanced participants’ long-term free recall, while having no effect on recognition memory. Also, females in the follicular phase of the menstrual cycle recalled more arousing than non-arousing words following stress exposure. These findings suggest that post-learning stress studies may serve as a model of traumatic memory formation and that post-learning stress exerts effects on memory that depend on female hormone levels.