Memories are packed into groups of neurons called engrams. Scientists from Canada studied how stress affects the work of engrams and focused on the amygdala, a part of the brain that is involved in stress and emotional reactions. The findings of the study are published on the Nature website.
The team worked with mouse models that were either injected with the stress hormone corticosterone or placed in a stressful environment for 30 minutes to allow the hormone to rise naturally. The rodents were then placed in a safe chamber with a neutral sound signal, and after a while in another chamber with a louder sound that ended with a blow to the limb.
After the stressful events, the mice responded to both sounds with apprehension, freezing in anticipation. “This means that they could not distinguish between neutral and traumatic events,” the authors commented.
When the scientists visualized the activity of neurons in mice, they found that when stressed, the rodents formed engrams for both events, which were activated by both sounds. Further observations showed that this was due to increased activity of the neurotransmitter endocannabinoid, which disrupts the natural blocking of certain molecules released by neurons.
There are now drugs that block glucocorticoid receptors. In current experiments, they have already helped mice reverse the effects of stress on memory formation. In future studies, the scientists intend to create more targeted drugs to minimize the risk of side effects.
In addition to drug development, further research should also show whether other mechanisms exist to mitigate the effects of stress on memory. The results could improve the treatment and prevention of anxiety disorders and post-traumatic stress disorder.
Previously, other studies have shown that sleep deprivation and marijuana use sharply increase the risk of anxiety.
