They say that the brain has unlimited memory, but judging by recent research, Sherlock Holmes was right after all, and we don’t have much space to store memories.
The study was conducted by scientists from the European Laboratory of Molecular Biology and the Pablo Olavide University in Seville. An article about the discovery was published in the journal Nature Communications.
“For the first time, we have recorded a pathway that is associated in the brain with the process of forgetting, active erasure of memories,” says Cornelius Gross, head of research at ELMB. It turns out that when we learn something, in parallel with the assimilation of new information, the brain also actively forgets the old one.
At the simplest level, learning involves creating associations and memorizing them. Working with mice, Gross and colleagues studied the hippocampus, a department in the brain that has long been known to help form memories. Information enters it through three main pathways, and when memories are strengthened, the connections between neurons along the main pathway become stronger.
When scientists blocked the main pathway, scientists found out that mice can no longer assimilate the conditioned reflex — they do not associate sound with a subsequent event and do not predict this event. However, if the mice learned the reflex before blocking, then they could still access the memory, and this suggests that access to the already formed memory goes through a different route.
But blocking the main path turned out to have interesting consequences: the connections along it began to weaken, that is, memory began to fade.
“Such a simple manipulation should not have led to such a result,” says Agnes Gruart from Pablo Olavide University. “When we started doing further research, we found out that the connections between neurons are weakened due to activity in another pathway.” It is also interesting that such forgetting occurs only in cases when the learning process is going on in parallel. When scientists closed the main pathway to the hippocampus under other circumstances, there was no weakening of the connections. “One explanation for this process is that the brain has only limited space to store memories and learned information, so when you learn, you need to loosen some connections to make room for others,” says Gross. “To learn new, you need to forget something old.”
Although the studies were conducted on mice, scientists from the European Laboratory have demonstrated that they can create a drug that activates the mechanism of “forgetting” in the brain. This approach, according to biologists, can be interested in the case when we want to help people forget about some traumatic memories.