Contextualization after stress: role of corticosterone and potential relevance for PTSD

Binding information to the context in which It is perceived promotes the recognition of information when later presented in the same context (contextualization). This is stronger for neutral than emotional content, since the latter distracts subjects from forming a link. We hypothesized that the ability to contextualize information under stressful conditions may protect individuals from generalization and hence render them more resilient to developing PTSD in the face of trauma. To test this, healthy male (human) subjects were first exposed to a contextualization test, 30 or 210 min after exogenous delivery of hydrocortisone (or placebo). Rapid and late hydrocortisone effects suppressed and enhanced respectively contextualization of emotional content. Contextualization of neutral content remained unaffected. Next, we tested individuals for contextualization directly or 2 hrs after psychoscial stress. Neutral conditions were more contextualized 2 hrs (than directly) after stress, while there was no effect for emotional content. A similar discrepancy between stress and hydrocortisone delivery was earlier observed in relation to intertemporal choice, indicating that cortisol may contribute to but cannot be equated to stress-related consequences on cognition. To examine the predictive value of contextualization for the vulnerability to PTSD, we reverted to a rat model, in which post-trauma PTSD-like behavior was observed in ~20% of the subjects. As predicted, pre-trauma contextualization inversely correlated with post-trauma PTSD-like behavior, but only in the non-stress group. These findings highlight the importance of contextualization in relation to stress and trauma but also emphasize differences between hydrocortisone administration and stress in humans and rodents.