Brain on Stress Fails to Learn Properly
Nick Hobson Ph.D. :
It's the end of the term, and you're ready to face the big final exam you've been studying for all month. You've gone to every lecture, read every chapter, and memorized every formula and key term there is to know. You've never felt more confident about a test before.
The big day arrives. You're feeling a bit anxious. The test booklet lands in front of you - and panic sets in. You try to brush it off, but to no avail. Sitting with pencil in hand, you turn over the page of the exam booklet. You read over the first few questions. It happens: All the knowledge you thought you had in your head magically vanishes from your mental repository. There's nothing up there. Nothing at all. It's as if someone went into your brain and removed all traces of your prior learning.
You end up failing the test, despite all the preparation beforehand.
It's a common occurrence because our ability to retrieve and encode information from stored memories can be quite easily hijacked by stressful situations. Stress has been shown to annihilate our ability to retrieve old memories. It offers a brain-based explanation for why we so often blank out during these types of memory-related performances.
How and why does this happen, exactly? And, perhaps more important, how can we overcome stress? Recently, a team of neuroscientists sought to uncover the neural underpinnings of stress, learning, and memory retrieval.
The neuroscience of memory
What we know currently is that our memories can be altered when presented with memory-related information, which makes these memories highly malleable. The brain's medial prefrontal cortex (mPFC) is responsible for detecting whether or not incoming information is in any way related to such stored memories.
So what happens when we are presented with completely new information that doesn't relate to any of our current memories? Brain scientists have found that new information is handled by a completely separate brain region called the hippocampus.
The role of the hippocampus in processing new information for memory function leads to a number of interesting hypotheses. Recently, it led one team of neuroscientists to further examine the role of stress in integrating new information and past memories.
The study and findings
The method to test their hypotheses worked as follows. The researchers used a task specifically designed to provoke stress in a laboratory setting. The task simulated a 15-minute job interview, which included a public speaking portion in front of a group of stern-faced evaluators.
Fifteen minutes after being stressed out, participants were required to learn two different types of information. One type was related to memories they already held, and the other represented completely new information. The researchers observed changes in their brain activity using functional magnetic resonance imaging (fMRI) while they learned the two types of information.
The scientists found increased activation of the medial prefrontal cortex (mPFC) while the participants engaged in memory-related learning. Also in line with their hypotheses, the hippocampus lit up while participants worked though novel information processing. Most important though, they also found an impairment in mPFC activity during learning when participants were placed under stress. Ultimately, this failed functional connectivity in the brains of stressed participants predicted poorer performance on the task.
Overall, the NeuroImage study provides a neural explanation for why we observe altered learning and memory abilities when we are faced with stress. In line with the current stance on learning and memory science, the authors found increased brain activity in the mPFC when participants were asked to learn memory-related information. On the other hand, novel information was associated with increased hippocampal activity.
Most relevant, however, were the findings that stress led to a substantial decrease in mPFC activity while processing memory-related information. These stress-induced changes in brain activity could help explain how stress seems to disrupt the use of prior knowledge to facilitate memory-related tasks (such as those required when writing a final exam).
This research has the potential to aid in our understanding of cases involving stress-related mental disorders where patients report distorted memory functions, such as generalized anxiety disorder (GAD). Furthermore, it could have crucial implications for areas exploring educational settings where stress plays a significant role in performance.