Why do we remember old memories so well even after years? Study suggests sleep could be responsible

Understanding how the brain manages to safeguard our memories could help experts design new treatment strategies for Alzheimer's


                            Why do we remember old memories so well even after years? Study suggests sleep could be responsible
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Ever wondered why old memories stay intact even after years? According to a new study, we may have to thank a good night's sleep for it. The brain could be actively replaying memories during shut-eye, thereby preventing older ones from being forgotten, the researchers predict. The finding paves the way for designing new treatments targeting memory loss.

Take sports, for instance, tennis and golf requires players to engage the same muscles, but differently. "Sleep makes sure that learning golf does not erase how to play tennis and makes it possible for different memories to coexist in the brain," Dr Maksim Bazhenov, lead author of the study and professor of medicine at UC San Diego, said. 

"Our memories are arguably one of the most important aspects of our lives. They help guide our decisions and ultimately define who we are as individuals," the researchers involved in the study told MEA WorldWide (MEAWW). "But we still do not fully understand how they are formed, stored, and protected from damage," they added.

Understanding how the brain manages to safeguard our memories could help experts design new treatment strategies for the elderly suffering from memory loss, people with learning disabilities, and other neurological or psychiatric disorders, they explained. 

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So the researchers in this study used a computational model designed to mimic different brain states: sleep and awake. The model helped them predict how sleep allows us to learn something new, while still keeping old memories from getting eroded.

"We predict that during the sleep cycle, both old and new memories are spontaneously replayed, which prevents forgetting," Bazhenov said. Reorganizing of memories in the brain ensure that new recollections do not degrade old ones. For all of this to happen, we need to get our dose of sleep, he added.

It is this skill that sets us apart from Artificial Intelligence (AI) -- that powers self-driving cars like Tesla, Apple's Siri, and Amazon's Alexa or even facial recognition. An AI that is trained to distinguish between pictures of cats and dogs will be able to learn a new skill like how to tell cars apart from trains after training, but at the cost of forgetting its first skill of separating cats from dogs. "Animals and humans, on the other hand, do not suffer from this limitation," the researchers explained. "We may need to add a sleep-like state to the computer and robotic systems to prevent forgetting after new learning and to make them able to learn continuously," said Bazhenov.

Memory defects in Alzheimer's disease or learning disabilities could be down to issues with replaying memories during sleep (Getty Images)

How is this related to memory problems?

Memory defects in Alzheimer's disease or learning disabilities could be due to issues with replaying memories during sleep, the team speculates. Besides, studies have shown that Alzheimer's patients have disturbed sleep patterns, which may "disrupt memory reactivation and lead to forgetting. More research is needed to explore these questions," the research group said.

In the future, scientists may be able to test stimulating the brain through sound or electricity to reduce memory impairments. The researchers also want to learn why memory gets activated at set times during sleep. They hope that understanding this could feed into developing potential treatments for the elderly, epileptic patients, and other neurological and psychiatric disorders.

The study is published in eLife.

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