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It’s happened to everyone: you study hard for weeks, you’ve got everything covered, but then on exam day — you fail miserably. You just can’t remember what you studied the night before or it’s all very fuzzy, to the point that you start confusing and mixing subjects. The problem is, of course, stress, which interferes with our ability to retrieve and encode memories. In a new study, researchers at the University of Hamburg in Germany have learned how exactly all of this pans out in the brain.

In recent years, the brain’s medial prefrontal cortex (mPFC) function has emerged as a key area of study for understanding higher-order memory and decision-making processes. It’s a large, functionally diverse region, whose intimate connectivity with the medial temporal lobes (MTL) may underlie its involvement in a multitude of memory-related tasks. For instance, one of its functions is to decide whether or not incoming information is in any way related to stored memories; e.g. “is this exam question related to anything I have studied?” When brand new information needs to be processed, this is handled by a separate brain region called the hippocampus.

The German psychologists wanted to investigate how stress interferes with both of these brain regions, looking for the neural basis of stress-induced learning impairment. During an experiment, participants pretended to attend a 15-minute job interview, which also involved public speaking in front of an intimidating-looking jury. After being exposed to the stressing episode, each participant was tasked with learning two different types of information. The first task was related to information that was already known, while the second represented completely novel information. During the tasks, researchers recorded the participants’ brain activity with functional magnetic resonance imaging (fMRI). 

When the participants learned new information that was related to stored memories, activity increased in the medial prefrontal cortex (mPFC). When completely new information was acquired, the hippocampus lit up. But when they were under stress, mPFC activity became impaired — and this functional connectivity problem predicted poor performance on the task.

These findings explain how a stressful event can disrupt our ability to access prior knowledge or perform memory-related tasks. On a more practical level, the study could help practitioners develop new therapies and techniques aimed at cases of stress-related mental disorders, such as generalized anxiety disorder (GAD). Furthermore, professionals working in education, such as teachers, professors, or coaches, could use these findings to devise new ways of mitigating stress to enhance performance.

Perhaps, the most important takeaway here is that stressing over a memory-dependent outcome can have catastrophic consequences. Before an important exam or job interview, perhaps it’s wiser to destress, wind down, and relax, instead of trying to cram up as much new information as possible.