A person's memories are supplemented throughout life, as we experience new events. In addition, old memories can change for one reason or another, for example, a person remembers some new details or receives new information about an event. That is, the same memories are sometimes “transformed” throughout life. Previously, scientists believed that such “plasticity” is associated with changes in brain cells that “rewrite” information. That is, it was assumed that old memories are deleted and new ones are written in their place. However, according to recent studies, the brain works with memories in a completely different way, and creates three copies of memories at once.
The brain may create three copies of memories at once. Photo credit: bbc.com
How the brain works with memories
A recent study by scientists was conducted on mice. After the rodents performed various tasks, the team monitored the activity of different groups of neurons in the hippocampus. The tasks included learning to avoid unpleasant situations, such as electric shocks to the legs.
Recall that this part of the brain is responsible for memory and learning. Thus, by monitoring the activity of neurons, the scientists could understand how mice form recently acquired memories at the cellular level and which neurons are responsible for them.
Scientists have studied how memories are formed in mice. Photo source: excelpestservices.com
According to a study published in Science, the brain uses three groups of neurons to store memories, which differ in the time of their creation, the degree of plasticity, and also the “strength of memory.” At the very first stage, when the memories are still very fresh, so-called “early neurons” appear in the hippocampus of mice, which are responsible for storing a long-term copy of the memory. This memory is weak, but over time it becomes stronger.
After some time, neurons of the second group, or middle level, appear. They are initially more stable. Then, after a certain amount of time has passed, “neurons of late origin” are formed, which, according to scientists, encode “strong copies of the memory.” However, over time, their strength begins to weaken.
In other words, the researchers found that the brain first creates one copy of the memory, then a second, and after some time, a third. Each copy, accordingly, is responsible for its own specific group of neurons. All, according to the researchers, work on different time scales.
Scientists have discovered three types of neurons that are responsible for different copies of memories. Photo source: naked-science.ru
This system of memories can be imagined as three different files on a computer. First, the brain creates an early, that is, the very first file, then creates a copy of it and works with it, and after some time, it creates a third copy of the file, but all previous files continue to be stored, at least for some time.
Why does the brain create three copies of memories
The study's authors believe their discovery may explain how the brain regulates memories over time. It's not yet clear how these neurons interact with each other, though. But the scientists did find that memories stored in the latest neurons are the most flexible and malleable.
This may mean that when memories are still very fresh and stored in the first group of neurons, they are stable and undistorted. True, it is quite conditional to say “undistorted”, since it is known that memory distorts events in the first seconds. But over time, when memories are stored for a long time, they begin to be more easily distorted by new information. True, the study does not say anything about when and how the transition from the early copy of memories to the middle and late ones occurs.
New discovery may help treat memory loss and PTSD. Photo source: peptid.ru
Will scientists be able to treat PTSD and memory loss?
It is still too early to say that the human brain works with memories in the same way as the mouse brain. However, if this assumption is confirmed, scientists will be able to develop new methods of treating various disorders and diseases associated with memory.
For example, with post-traumatic stress disorder (PTSD), people are tormented by unpleasant obsessive memories of events that caused psychological trauma. Perhaps scientists will be able to develop drugs that will help deactivate early-born neurons and activate late ones, which are less stable and therefore more susceptible to psychotherapy. As we have previously said, poor memory is not a flaw of the human brain, but a feature we need that helps us get satisfaction from life and generally feel well.
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Memory loss can also be treated in a similar way. That is, if a person has problems with late neurons, theoretically, drugs could activate an early copy of memories. As mentioned above, the brain stores three copies at the same time. Therefore, scientists will only need to learn how to somehow switch between them. But for now, these are all just assumptions.