Childhood memories, where do they end up? Do they disappear completely or remain “forgotten” somewhere in memory?

The disappearance of childhood memories is a phenomenon considered obvious, which is of interest to researchers because represents a model of how and why the human mind forgets or remembers. In fact, the idea that very early memories are actually reconstructed on the basis of photographs, films, stories from parents or older sisters/brothers. It is only around the age of seven that memory matures enough to ensure stable memories. Before that age, the function of long-term memory is perhaps not considered a priority by the brain, which is engaged in tasks that are more important at that moment than remembering, such as understanding the functioning of the surrounding world.

The review in Science

The magazine dedicated a review to infantile amnesia Science, with a review of some of the ongoing research. One of the most interesting aspects of the new research is the possibility that memories of early life may not be gone forever. For example, a study on mice, published in the journal Science Advances and coordinated by Tomas Ryan, shows that, if during pregnancy the mother receives a stimulation of the immune system, an altered state is generated in the fetus's brain which turns off certain specific biological “switches”, whose task would be precisely to cancel the memories of the early years from my mind.

The “switches”

The reason for the existence of these “switches” is not yet clear. Their task doesn't seem to be help “make space” to subsequent information, since the brain could store much more data than it retains. In fact, to form a memory the brain resorts to the creation of a limited network of neurons that communicate with each other, the so-called “engram” whose possible number is incredibly high.

The engrams

Every time information is retained it means that an engram has formed, which happens mainly in an area of ​​the brain called the hippocampus. But it is still a labile memory, until there is an initial stabilization, with the formation of new synapses between those same neurons, a phenomenon for which the activation of genes is necessary for the synthesis of new proteins. Then the brain will continue to stabilize the newly formed memories without the knowledge of consciousness, making “offline repetitions” of them when the owner of that brain is sleeping or in any case when he is not using it fully.

Research in the laboratory

To literally try to shed light on the definitive disappearance or permanence of “forgotten” memories, neurobiologist Paul Frankland of the Hospital for Sick Children at the University of Toronto coordinated research on newborn mice, this time using optogeneticsa technique that allows cells to be selectively activated or deactivated in vivo through a light beam of specific wavelength.

His research group used genetically modified mice, capable of producing a specific light-sensitive protein in the neurons of the hippocampus, involved in the formation of memories, which can therefore be activated with optogenetics. Then the mice were taught to fear the arrival of a small electric shock when they tried to approach the food placed in a specific box.

After a month, when the mice demonstrated that they had forgotten the existence of the possibility of receiving the shock, with optogenetics they stimulated that area of ​​the hippocampus, thus seeing reappear the memory that seemed lost. The mice suddenly remembered the possibility of the electric shock and avoided going near the food.

Electroencephalographic indicators

Now new research, not only on mice but also on humans, will try to identify specific electroencephalographic indicators that indicate the formation and dissolution of engrams, so as to be able to follow the development of memories and their “loss”, perhaps only apparent. With the possible aim of reactivating them. An interesting development not so much for the recovery of childhood memories, but for attempting to improve the initial memory losses that occur at the onset of some forms of dementia.

Freud's theory: little ones must forget “by force”

It was already known that childhood memories disappeared from the mind before anyone became interested in the phenomenon Sigmund Freud, who spoke about it in several writings, including the «Three essays on sexual theory». But according to Freud, infantile amnesia was not simply due to the functional inability of children to register facts and impressions, but instead had a precise significance in the process of psychological development.

In fact, according to his theorization, children had to forget that period of their lives, as it corresponded to one psychologically turbulent phase, in which problematic infantile sexuality was active. In fact, in the early years the child would have found himself involved in the so-called Oedipus complex (or Electra for girls), when a sexual interest towards the parent of the opposite sex and a competitive conflict with the parent of the same sex would have been active. A concept that today is considered by many to be revised.

The problem caused by underdeveloped hippocampus

In addition to the psychoanalytic one, there are cognitive psychological theories and theories that take neurobiological aspects into account to explain childhood amnesia.

According to the cognitive theories the forgetfulness of the first years of life would be due to the fact that the brain is not yet capable of generating the very sense of the existence of a Self to which the memories should belong. It would play a role too insufficient language development, fundamental for the creation of memories, which must somehow be associated with words or a verbal story.

According to some neurobiological theoriesthe problem would on the contrary be of a structural nature, being caused by a still poorly developed hippocampusincapable of adequately processing the information intended to be codified and stored, a necessary step so that it can then be recalled to memory.