The formation of false memories associated with mechanisms for updating memory

(ORDO NEWS) — Imagine: you return home late in the evening, turn into a dark alley – and suddenly someone abruptly attacks you from behind. While you have time to realize what happened, your valuables have already been stolen, and the attacker has disappeared. The event makes you such an indelible impression and is terrifying that now you are afraid to walk alone in the dark.

At times like this, when the brain tries to comprehend sudden or traumatic events, we often create poorly formed memories that can then lead to confusion or even post-traumatic stress disorder (PTSD). Subsequently, it may not let a person go for years, accompanied by all kinds of “triggers”, resurrecting terrible memories, even if they are new situations that remind of bad things, they are completely safe.

Neuroscientists from the University of Technology, Sydney (Australia), using new behavioral, molecular and computational methods, carried out a comprehensive analysis of poorly formed unpleasant memories and the mechanism of how the brain operates with them. The theoretical model showed how a person may have this common fear (when, for example, he fears places reminiscent of bad experience).

“For the memories to be useful, they must be correctly formed during the event, that is, they must accurately reflect what actually happened. However, in the real world, many memories may be inaccurate, especially in situations where the experience was short, sudden, or extremely emotional, which can often occur during trauma. Inaccurate memories can occur when memory is poorly encoded. This can be explained by subtle differences in how each person processes memories, or by the effects of diseases such as Alzheimer’s and dementia, ”explains Bright Wissel, Center for Neurobiology and Regenerative Medicine, lead author of a paper published in Current Biology.

As part of the experiment, rodents were placed in a specific space for 30 seconds, and then they were suddenly scared. After that, the animals were taken to another place, which was similar to the first, but did not carry any danger for them: getting there, the experimental subjects died away from fear for half an hour, paralyzed in anticipation of being scared again.

According to scientists, this is due to the fact that the mice, like the person who survived the attack in a dark alley, did not have enough time to properly process the environment before they got a negative experience and were scared. Such poorly formed memories meant that the brain could not distinguish between a dangerous space and a safe one. However, when the mice were placed back to their original environment, where they experienced a “terrible memory”, they moved freely and carefree explored everything around.

“The same process may in some cases lead to incorrect memory updates. We also identify one molecular mechanism called reconsolidation (in which new information and knowledge help to recall already existing knowledge. – Ed.), Which could be a mediator in this process. <…> This suggests that we could purposefully work on such renewal mechanisms for the treatment of memory disorders and anxiety disorders when memories are poorly formed,” adds Dr. Rafael Zinn.

Thus, a mechanism that updates bad memories can seriously distort them. When the mice froze in fear, falling into a reminder of a bad space, their brain updated the hazy memory of the initial traumatic experience with new – incorrect – data. By the time the rodents were again placed on an environment where they were scared, their memory was already “refreshed” by false information that made the animals think that they were safe.

That is, when a person has already formed memories associated with some bad moment in his life, the brain reactivates them in a subsequent similar situation – and updates it. Sometimes a poorly formed memory can be mistakenly activated in a similar, but irrelevant situation. Then the brain updates the old memories, making them wrong, false – instead of creating new and completely different memories of the new situation.

“The context in which sudden terrible events occur can be poorly encoded in memory. <…> An update in a similarly safe context mistakenly transfers fear from a dangerous to a safe context. We argue that these phenomena can be explained by the uncertainty of where the events occurred. In addition, we show that the hippocampal-cortical neurocomputer model based on this assumption successfully models and explains our observations. The results show that context-poor memories are non-adaptive and can be improved or distorted afterwards, which is important for the basic theory of memory, memory distortion, and the treatment of disorders such as post-traumatic stress disorder,” the researchers write.

The authors emphasize that although the results were obtained on mice, their findings can be applied to many animals with a developed brain, including humans. In addition, the work offers a basis for studying various therapeutic approaches for injuries and anxiety disorders, as well as for dementia, which is characterized by a clear inability to form true memories. And in the future, the findings can be taken into account when analyzing the testimonies of victims of crimes in court.


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