Why do we forget our first memories? Scientists already have the answer

What’s your first memory? Perhaps a birthday party, a beach vacation, or a hug from grandpa that happened after you turned two. Before this age, we were aware of our surroundings and recorded memories, just like we do now. But, for some reason, over time we lost them. This phenomenon is known as childhood amnesiawhich occurs in the vast majority of people. There is an exception though. It has been noticed that people with autism spectrum disorder (ASD) They have a greater tendency to remember very early events from their childhood. It is unknown what causes childhood amnesia and why it does not occur in ASD. However, a new study reveals a possible guilty on the table: the immune system.

Research published in Science achievementswas carried out in mice, They have also been observed to develop childhood amnesia. It is logical that they cannot talk about their memories. But when it’s done to them remember the conditioning, they usually lose it if it happened very early in their life. Therefore, they were ideal candidates to find out why we forget our first memories

The authors of the study, Trinity College Dublin, decided to analyze the role of the maternal immune system, since it is a critical component of the environment in which embryos develop, and also a factor that must be considered in the occurrence of ASD. They conducted several experiments step by step and found out what could be the cause of childhood amnesia. At least how can this be avoided. Now we just have to understand why there is so much forgetfulness.

This is how memories are remembered

Now what Inside out back in vogue with the arrival of the second part, it’s time to watch the original film again. In it you will see how a girl’s mind works: from how she controls her emotions to how he stores memories.

Hidden in the mind of a girl named Riley is a huge warehouse with shelves full of marbles, on which you can see each of her memories. These little balls, although logically they do not exist as such, can be compared to real-life structures known as engrams.

By definition, this neural structures stable responses that are generated by stimulation, external or internal, and are associated with the activation of specific responses that may be conscious or unconscious. In other words, these are special neural connections that, when activated, reproduce the subjective experience for which they were created. Like a little record of experiencewhich is stored in memory.

These engrams may remain stable and easily accessible, like when all of Riley’s memories were laid out on the shelf. But the connection with them can also be lost, preventing them from reactivating, as when the memory of Riley’s invisible friend, the pink elephant, It is disposed of as garbage.

In the film, the erasure of this memory is an example of childhood amnesia. How, as a girl grows up, she begins to lose memories of her early childhood. But why is all this happening?

The immune system and childhood amnesia

The authors of the new study wanted to test the role of the immune system in childhood amnesia mice. To do this, they conducted several experiments, which began with pregnant female mice. Just like it happens in humans, sometimes during pregnancy maternal immune response to the fetus. In the experiment, these reactions were induced and controlled to separate mice born to mothers who responded in this way from those who did not.

After that, all of them were given the answer: fear of minor electric shock. Over time, those exposed to their mother’s immune system developed some of the symptoms associated with ASD, but were also able to remember longer what happened when they were shocked. On the other hand, those who have not been exposed to the immune system They quickly forgot about it.

At the next stage of the experiment, genetic mice were obtained with a gene that marks neurons associated with memory. This way you can see from the outside how they develop. Thanks to markedsaw very significant changes in the size of the engrams of mice whose mothers were stimulated to produce an immune response during pregnancy.

It was already clear that the immune system had something to do with this. But this system consists of many components, so it remained to find out which of them influenced the development or not of childhood amnesia. There were several candidate components, so transgenic mice were produced without each of them and the effects on their offspring were observed. Those that did not have protein were called cytokine IL-17a They were the ones who helped find the key. And even when the immune system was activated, the mice experienced childhood amnesia.

Why do we forget our first memories?

In short, according to the mechanism almost all of us have childhood amnesia. Only those who were exposed to a maternal immune response during pregnancy that involved the IL-17a protein are free from this effect.

This means it likely provides us with some evolutionary benefit, which is why it has persisted in our species. But what is this benefit? This question remains unanswered. The good thing is that now that we know how to undo it, it will be easier to pull the thread. Plus maybe one day we’ll have the key to dive into memories and find that first hug from a mother that for some reason our brain insists on forgetting.