Cortisol May Strengthen Frightening Memories

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While strong memories of stressful experiences are common, they tend to fade over time. In some cases, however, such as with posttraumatic stress disorder (PTSD), these strong emotional memories persist. According to newly published data, the stress hormone cortisol may be to blame.

More specifically, the results suggest that cortisol has a strengthening impact on the consolidation of memories, or the several-hour process in the course of which a memory is formed immediately after the experience.

Additionally, cortisol appears to affect memories in humans during reconsolidation, or the consolidation of memories occurring after memory retrieval, with data indicating that cortisol can enhance this process, researchers from Bochum, Germany, found.

For this study, the researchers observed participants on 3 consecutive days. On the first day, the participants experienced an association between specific geometric shapes and an unpleasant electric shock. On the scond day, some participants received a cortisol pill and others received a placebo. Once again, they were shown one of the geometric shapes associated with the electric shock. On the third day, the researchers assessed memory for the geometric shapes.

Participants who received the cortisol pill remembered the fear-associated shape particularly well, the researchers noted. This was demonstrated by heightened skin conductance, which is an established measure for emotional arousal.

"The results may explain why certain undesirable memories don't fade, for example in anxiety and PTSD sufferers," study researcher Oliver T. Wolf, PhD, of Ruhr-University, Bochum in Germany, said in a press release. 

For instance, if a person recalling a frightening event has a high cortisol level, the memory will be strongly reconsolidated after each retrieval, the researchers concluded.

Cortisol May Strengthen Frightening Memories
Cortisol May Strengthen Frightening Memories
The return of conditioned fear after successful extinction (eg, following exposure therapy) is a significant problem in the treatment of anxiety disorders and posttraumatic stress disorder (PTSD). Targeting the reconsolidation of fear memories may allow a more lasting effect as it intervenes with the original memory trace. 

Indeed, several pharmacological agents and behavioral interventions have been shown to alter (enhance, impair, or otherwise update) the reconsolidation of reactivated memories of different types. 

Cortisol is a stress hormone and a potent modulator of learning and memory, yet its effects on fear memory reconsolidation are unclear. 

To investigate whether cortisol intervenes with the reconsolidation of fear memories in healthy males and how specific this effect might be, we built a 3-day reconsolidation design with skin conductance response (SCR) as a measure of conditioned fear.

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