2023-12-17 08:37:03
by Danilo Di Diodoro
New techniques for studying the brain and the genes involved in memory could make it possible to “reactivate circuits” in which information that would otherwise be inaccessible is stored. This is indicated by research (for now) on mice
Where do the memories of the first years of life go, which no one can recover? An answer to what happens to those memories comes from research carried out on mice, because they also forget their first experiences, thus providing an experimental model to neurobiologists, who in their laboratories regularly see the information that the mice had learned disappear from memory. shortly after birth.
Immune system
A new study published in the journal Science Advances indicates that, in reality, the disappearance of these early memories would not be mandatory since under certain conditions it may not even happen. In particular, it does not happen if the mother receives a stimulation of the immune system during pregnancy. According to Tomas Ryan, co-author of the research, this immune activation during pregnancy causes an altered state of the developing brain and turns off specific biological switches whose task is to erase memories of the first years of life from the mind.
The study is important because it sheds light on a mechanism of childhood forgetfulness that until now had not been fully understood and which probably has connections with the subsequent development of some mental disorders. But it doesn’t resolve the question of why the brains of mice, and humans, at some point erase those early memories.
Engram
Today neurobiologists know that the problem does not seem to be making room for subsequent information, since, due to the way the mechanism of memory formation works, the brain could store much more information than it retains. In fact, to form a memory, the brain creates a small network of neurons that communicate: it is the minimal neurobiological basis of memory, also known as an engram. Every time information is retained it means that an engram has formed, a process that initially occurs mainly in an area of the brain called the hippocampus.
Stabilization
But it is still a labile memory that risks fading until an initial stabilization occurs with the formation of new synapses between those same neurons. It is the phenomenon of neuroplasticity: information is stabilized because new points of contact and electrochemical exchange open between those neurons, a phenomenon whose realization requires the activation of some genes to start the synthesis of new proteins.
Reinforcement
Now that information is ready to be retrieved even after some time, at the service of learning and memory. Of course, as anyone with experience studying knows, repeated exposure to that specific information strengthens the process and further solidifies it.
Handling
But there is also another natural phenomenon that strengthens memory. The brain has learned to manipulate newly formed memories without the knowledge of consciousness, making “repetitions” of them when the owner of that brain is sleeping or in any case not using it fully. They are repetitions that could be defined as offline: the groups of neurons involved in newly acquired information take advantage of the “silence” of the brain to repeat and to strengthen their neurochemical links also with other areas of the cerebral cortex, thus helping to further stabilize them.
Optogenetica
The studies that led to a full understanding of these mechanisms were carried out using the recent technique of optogenetics, a complex method that is transforming research in neuroscience, allowing specific brain circuits to be “turned on” and “turned off”, verifying their respective behavioral consequences. Remembering information therefore means being able to activate that same group of neurons again, which is possible as long as the bonds that were formed when the information was fixed remain.
Perspectives
As everyone knows from experience, certain information, especially if recently archived or reactivated, is easily recovered, others only with difficulty. Often you have the sensation and even the certainty of having that specific information you are looking for, but you cannot find it. It means that those bonds, that engram, are slowly dissolving and only a new repetition will be able to fix it again for a little while longer. In light of all this, it could sooner or later even become possible, through techniques such as optogenetics, to reactivate and consolidate, or on the contrary erase, specific memories.
But forgetting is also necessary
The brain needs to forget, because due to its complexity it must make a continuous selection among the information it receives in order to be able to use only that necessary to “navigate” the world and imagine the immediate future. “Memories could be better defined and understood as models of the future,” say the authors of the study published in Science Advances.
«Once a memory is no longer useful for predicting what the immediate future might be like, it becomes convenient to forget it. So forgetting happens passively, but it can also be an active process. It has been hypothesized that the natural tendency of neural systems is to let information degrade rather than preserve it.” Active forgetting is therefore fundamental for mental balance, decision-making ability and mental health. This model is becoming even more complicated with the discovery that other brain cells with mainly immune functions can also be involved in the processes of remembering and forgetting.
Only children see the world “as it really is”
Sight is not just the perception of external stimuli, but is influenced by memory: the vision of the world is the result of the fusion of these two elements. Research published in Cognitive Science by Israeli and American psychologists indicates that this phenomenon is much more marked in adults than in children. It is as if children were able to perceive environmental stimuli in a more basic way, without interference from memory and previous experiences.
“Our experiment provides new evidence on how the interaction between memory and perception changes over the course of life,” say the researchers from the School of Psychological Sciences at Tel Aviv University. “As we gain experience, in this case with visual perception, but the same is likely to happen in other domains, we tend to make more use of previous experiences and less of actual perception.”
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December 17, 2023 (changed December 17, 2023 | 07:36)
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