Memories are packaged into groups of neurons called engrams. Canadian scientists studied how stress affects engram function and focused on the amygdala, a region of the brain involved in stress and emotional responses. The study's findings were published on the website Nature.
The team worked with mouse models: they were either injected with the stress hormone corticosterone or placed in a stressful environment for 30 minutes to allow the hormone to naturally increase. Afterward, the rodents were placed in a safe chamber with a neutral sound signal, and after a short time, in another chamber with a louder sound, ending with a shock to the limb.
After stressful events, the mice responded to both sounds with apprehension, freezing in anticipation. "This suggests that they were unable to distinguish between neutral and traumatic events," the authors commented.
When scientists visualized the activity of mice's neurons, they discovered that under stress, the rodents formed engrams for both events, which were activated by both sounds. Further observations revealed that this was due to increased activity of the neurotransmitter endocannabinoid, which disrupts the natural inhibition of certain molecules released by neurons.
Today, drugs exist that block glucocorticoid receptors. In ongoing experiments, they have already helped mice reverse the effects of stress on memory formation. In future studies, scientists plan to develop more targeted medications to minimize the risk of side effects.
Beyond drug development, further research should also reveal whether other mechanisms exist to mitigate the effects of stress on memory. These findings could improve the effectiveness of treatment and prevention for anxiety disorders and post-traumatic stress disorder.
Previously, other studies have shown that sleep deprivation and marijuana use sharply increase the risk of anxiety.
