It is possible that you have noticed that stressful situations leave a greater imprint than those of peace and contentment on your memory. New research could be the answer.
Two schools of thought had previously been held about this. One was that the brain stored these stressful memories in a different way than the other. The latest study supports the second theory.
It seems that stress can play a role in the recall of these memories. These memories seem to be more distinct than others created during the same stressful episode.
Oliver Wolf, a neuropsychologist at the Ruhr University Bochum (RUB), in Germany, says that "we usually have detailed images within our mind's eye of stressful events, such as driving the test."
"Whereas a stroll through the park on the exact same day is quickly forgotten."
Researchers set up a mock job interview for two interviewers to find out the reason. This is the Trier Social Stress Test and has been proven to be a reliable method of inducing stress in people (as you might imagine).
Part of the test is giving a presentation for the interview panel. They are instructed to keep their expressions neutral. 24 objects were also introduced to study participants during the same time period. These included a coffee cup and a clock, as well as a roll tape and a marker pen.
The interview was stressful for 33 people. 31 other people were given a more friendly version where they could talk about positive topics and the interviewers allowed to give feedback.
Functional magnetic resonance imaging (fMRI), scans were done to follow up. These scans focused on the amygdala, which is linked to emotional learning. Participants who had experienced the stressful test found that neuronal traces that were triggered when they saw objects during the interview were more similar than those that were triggered by objects not seen.
(Institut fr Kognitive Neurowissenschaft, Anne Bierbrauer)
Above: A part of the experimental setup with the interview panel.
The control group was not affected by this. It showed that objects that are remembered under stress are more closely related in terms of brain representation. The interview panel's faces triggered neuronal activity that was similar to those of objects remembered.
Nikolai Axmacher, RUB neuropsychologist, says that the stress was triggered by the committee members in the interview situation. It seems that the link between objects and stress triggers was critical for enhanced memory.
The study shows that emotional memories are more memorable because they have more similarities to the emotions experienced in our brains.
The hippocampus is a part of the brain that helps with memory and learning. However, items and contexts experienced in neutral emotions are bound to the hippocampus. Items and contexts experienced during high emotion seem to be linked in the amygdala.
Although this research was limited to one scenario, it is clear that the results point to a working hypothesis which can be extended to other situations.
These data could be used to study mental disorders such as memory problems. They also give us more insight into the brain's complex relationship with memory.
Anne Bierbrauer, RUB neuropsychologist, says that this result could help us better understand trauma and emotional memories.
Current Biology published the research.
