How does the brain win new memories

To forget has to be learned : Delete button in the brain

Solomon Schereschewski did not have to complain about a bad memory throughout his life. The Russian, born in 1886, had phenomenal memory. The journalist memorized speeches he had heard, word for word, as well as formulas and number tables or texts in foreign languages. Just anything that was presented to him. A dream? More like a nightmare.

Schereschewski could not forget, and that became a curse for him. He was literally inundated with the details of his memories, prevented from thinking by an avalanche of banalities. It's as if we could or have to recap at any time where we parked our car or bike in the last two years, what weather was 71 days ago and what we had for breakfast 28 days ago.

If you want to survive in everyday life, you have to erase the unimportant

A terrible idea! Conversely, this means: In order to survive in everyday life, you have to constantly forget the unimportant. Even more: The delete button in the brain ensures that you stay mentally up to date.

For brain researchers Blake Richards and Paul Frankland from the University of Toronto, it is now well established that forgetting is just as important to our memory as remembering. "We have found a lot of scientific evidence that there are mechanisms for memory loss and that these are different from those involved in storing information," Frankland said, according to a press release. In the journal “Neuron”, the two researchers expand their thesis that memorizing and forgetting are necessary poles of an intact memory.

Why does the brain have to forget? To make room for new memories is an intuitive explanation. But it is not true, as the scientists point out. The brain has 80 to 90 billion nerve cells. If only a tenth of them were reserved for storing personal experiences, one could “file” a billion of these episodes, and if stored sparingly, even many more.

So forgetting is not a problem of insufficient storage space.

The past must not become a prison

Why then has evolution endowed man with such a sketchy and imprecise memory? Wouldn't it be much better to have everything registered on the biological hard drive in tiny detail? Richards and Frankland disagree. In a rapidly changing and confusing world, having a lot of concrete memories is a disadvantage. "Forgetting serves to adapt to a changeable environment because it enables flexible behavior," they write. Schereschewski, the memory artist, on the other hand, was walled in by his past.

If a lot of information flows into the brain, thinking and behavioral guidelines tailored to special situations are more of a disadvantage. Mental agility is important in such situations. Decisions should then be guided by general principles and experience rather than by little things from the past. What matters is the essential, the essence of what is experienced, not its details.

It looks different when the environment is "reliable" and little changes. Then detailed and concrete memory contents have their place. According to the motto: We have always done it this way! In any case, it is the interplay of permanence and impermanence that defines a functioning memory. It thus becomes an important decision-making aid.

What is learned is stored in networks

What happens in the brain when remembering? The memory itself is stored in a network of nerve cells connected to one another via contacts (synapses). The network was established at the moment of learning. If what has been learned is brought into consciousness, it is activated again. To put it simply: the stronger the contacts between the network nerve cells, the more vital the memory.

When forgetting, the opposite happens. Nerve contacts and networks are weakened. In addition, newly formed nerve cells come into play, for example in the hippocampus ("seahorse"), a memory center located in the depths of the temporal lobe. They "disturb" the already existing nerve networks and weaken memories.

“We don't remember days, but moments,” the scientists quote the Italian poet Cesare Pavese. “The richness of life is based on memories that we have forgotten.” Memory is not a perfect repository of what has been experienced and learned. Rather, it is a house that is constantly being converted and expanded: depending on who is currently living in it.

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