How stress affects the memory and causes anxiety
How stress affects the memory and causes anxiety
stress means that mice form large bundle of neurons in the brain that disturb memory formation and make them anxious to harmless situations 1 . This could explain why stressed people often seem threatened in safe environments.
researchers have long since found that stress or trauma can lead to people being afraid of harmless situations. After burning a finger on a hot pan, a stressed man not only hot pans, but also avoid the entire kitchen or cooking. This type of generalized fear can often be observed in people with post -traumatic stress disorder (PTBS) and in generalized anxiety disorders.
A study published in the magazine Cell today describes how stress the Memory Formation in particular disturbs the memory of fearful events. The results could influence the development of therapies for people with PTSD and anxiety disorders.
"This paper is really a masterpiece," says Ryuichi Shigemoto, neuroscientist at the Institute of Science and Technology Austria in Klosterneuburg. "They used so many different methods and techniques to demonstrate this long way."
Memorial packages: Memories are packed in groups of neurons, which are called engrams and are active when a memory is formed. Sheena Josselyn, a neuroscientist at the Hospital for Sick Children in Toronto, Canada, and her colleagues examined whether stress the formation of engramen distances , especially in a brain area that is known as amygdala and is involved in the reaction to stress and emotions.
The study included an elaborate three -stage experiment on mice. First, some adult mice were put in a stressed state by injecting the stress hormone corticosterone or for 30 minutes they were pushed into a small tube, which led to increased corticosterone values.
After that, the mice - some stressed out and others - were brought to a chamber in which a medium -high tone was played for 30 seconds, which was considered a neutral event. After a break, the mice returned to the chamber and experienced a high-frequency whistle for 30 seconds, followed by a 2-second shock on the foot to simulate an angly event.
To test how the mice stored the memories of these experiences, they were placed in a new environment and the two tones were repeated. The non -stressed mice mainly froze when they heard the high -frequency whistle, while the stressed mice reacted to both tones and pipe, which indicates that they could not distinguish between the neutral and the fearful event.
Exclusive Club: The researchers used various techniques to visualize the neuronal activity in the rodents. They found that the non -stressed mice during memory formation formed small engrams in response to the whistle and the foot shock, which were only activated if they were exposed to the whistle. The stressed mice, on the other hand, formed larger engrams that were reactivated in both tones.
Other experiments revealed the chain reaction in the brain, which led to larger engrams in stressed mice. Under normal conditions, certain neurons in the amygdala block neuronal activity through the release of chemical messenger substances, which are known as gamma amino acid (GABA). This ensures that a small engram is formed in response to a negative memory. "It's a bit like the velvet curtain in a night club: it only lets certain neurons in the night club," says Josselyn. In the event of stress pumping neurons, the brain is full with a neurotransmitter called Endocannabinoid, which binds to glucocorticoid receptors of the inhibitory neurons and prevents their GABA release, which leads to larger engrams. In other words, the velvet curtain falls and "many neurons can get into this exclusive club," explains Josselyn.
The team could undo the effects of stress on memory formation with two medication, one of which is approved to end an early pregnancy, Mifepriston. These drugs either block the glucocorticoid receptors or the production of endocannabinoids, so that the stressed mice could call up memories as well as not stressed mice. However, the researchers warn that the medication beyond the brain have side effects and are only effective if they are administered at the time of memory formation, so it will be unlikely to use for people.
Josselsryn and her colleagues are now trying to examine whether engrams can be changed after the memory formation or whether there are other ways to alleviate the effects of stress on memory.
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Lesuis et al., Cell 188, (https://doi.org/10.1016/J.CEL.2024.10.034) 2024.