Effects of stress and sex on acquisition and consolidation of human fear conditioning.

We examined the relationship between stress hormone (cortisol) release and acquisition and consolidation of conditioned fear learning in healthy adults. Participants underwent acquisition of differential fear conditioning, and consolidation was assessed in a 24-h delayed extinction test. The acquisition phase was immediately followed by an 11-min psychosocial stress period (arithmetic test combined with a public speech). Salivary cortisol was sampled at various time points before and after acquisition and retention of fear conditioning. Results showed two effects of endogenous cortisol. Post-acquisition cortisol correlated with fear acquisition in male but not female participants. In addition, post-acquisition cortisol correlated with consolidation of fear but only in those participants with high cortisol levels. We conclude that in the short term, a robust and sexually dimorphic relationship exists between fear learning and stress hormone levels. For those participants whose fear learning is accompanied by high stress hormone levels, a long-term relationship exists between cortisol release and memory consolidation. These short-term and long-term effects may relate to the differential involvement of mineralocorticoid and glucocorticoid receptor subtypes, respectively. The findings have implications for understanding the role of stress, sex, and hormones in different stages of fear learning and memory.