In a new study, scientists using C. elegans worms, a model organism for brain research, found that forgetting doesn’t reverse or erase changes in the brain that result from learning, as some theories suggest.
Instead, forgetting generates a new brain state that is different from the one that existed before the learning occurred or from the one that exists while the learned behavior is still being remembered. In other words, what is forgotten does not completely disappear and can be reactivated with a kind of initial jump.
“After forgetting, we can often remember what we learned before, and our brain is no longer in a naive state,” explained Yun Zhang, a professor of organic and evolutionary biology and a member of the Harvard Brain Science Center. “If we have a party and then several months later we really forget, ‘When did I have that party? Who attended?’ And then your friend can say, ‘Remember this and that. Remember that we sang a song for you’. Suddenly, you’ll remember, won’t you?
The research, published in Science Advances, sheds new light on how forgetting occurs in the brain at the systems level, and on the molecules that the researchers found appear capable of speeding up or slowing it down.
The foundation of the work could one day be used to understand mental health problems in which forgetting goes wrong, whether it happens too slowly or too quickly. It could, for example, hold clues to dealing with disorders such as post-traumatic stress, where aversive memories persist aggressively.
“The mechanisms provided by this study would give us entry points to think about what could have gone wrong with these neurological diseases,” Zhang said. “It helps us hypothesize about the molecules and processes involved, as well as the activity of neurons that are important for forgetting, and propose ways to understand the pathology of related neurological diseases.”
Forgetting is part of normal brain function due to the limited capacity of the brain. Much research has been done on how memories are formed, but less research has been done on the nature of forgetting or how it happens in the brain.
Why and how does the brain forget things?
Some studies suggest that when a memory is forgotten, it is simply erased and the learning is lost. Another possibility is that memory and learning become more difficult to access during the forgetting process but remain in some form.
The work of members of Zhang’s lab, led by postdoctoral scholars He Liu and Taihong Wu, and collaborators leans toward the latter theory. The researchers taught the worms to identify by smell and avoid a strain of infectious bacteria that makes them sick. But an hour later, the worms forgot. The researchers then analyzed the brain activity of these worms and the genes expressed in their nervous systems.
Comparing them to worms that had never learned the behavior or had just finished training, the researchers found that the neural activity and gene expression of the worms that forgot the behavior did not revert to the naive state from before, nor did they match the neural activity of the worms. the worms that had just been trained. They were different.
The scientists also looked at whether the worms that had forgotten the training could remember it, and the answer was that it seems so. Normally, it takes three to four hours to train the worms, but the ones being retrained completed the process in about three minutes. “There are still remnants of memory in his brain that can be awakened, that can be reactivated,” Zhang said.
The specialist and her colleagues plan to use this study as a starting point to further study the mechanisms of forgetting and how it may eventually be applied to mental health problems. “This is just the beginning to understand forgetting, a brain process essential for daily activities,” she concluded.
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Source: Ambito
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