Sleep and Brain Health

How the Brain Chooses Which Memories to Save

Have you ever wondered how your brain chooses which memories to cement into long-term memory? Why, for example, do we remember so many details from that family vacation but not what we ate for breakfast, say, the first Monday of last month? And how can we help increase the likelihood of a memory being stored permanently in our brain?

According to a new study on mice, it’s about tagging important experiences during learning to be moved to storage—and resting after the experience in order to allow cells in the hippocampus to “spark” in a specific pattern.

The Research

A team of neuroscientists from New York University studied the brains of mice as they went through a maze with a sugary reward at the end. Using electrodes implanted into the rodents’ brains, the researchers could monitor nerve-cell activity. They noticed that when mice reached the end of the maze and paused to eat the sweet treat, their brains sparked sharp-wave ripples. These ripples were repeated as many as 20 times and the daytime pattern was replayed during the night while the mice slept, moving the experience into long-term memory unconsciously.

On the flip side, experiences that produced few or no sharp-wave ripples were not converted into lasting memories.

Of particular interest is that there were bursts of activity when the mouse was standing still and the brain was “idling.” It’s believe that this post-event pause is what allowed the mice to move the reward-driven experience to long-term memory.

According to Columbia University Zuckerman Institute Director Daphna Shohamy, it’s common to see this behavior in animals—pausing during the day after a particularly rewarding experience to embed the memory. Shohamy worked on a similar study with human a few years ago in which the study participants navigated a maze looking for a treasure. Those who got the treasure were more likely to remember the random object they had passed en route.

Increasing the chances of an experience being remembered

The study’s senior author, Biggs Professor of Neuroscience at NYU Langone Health Dr. Gyorgy Buzsaki, says that anyone looking to cement an event into long-term memory should pause and relax immediately afterward to allow their brain to spark sharp-wave ripples. Dr. Buzsaki’s advice? If you watch a good movie want to remember, don’t immediately follow it with another movie or TV show. Instead, go for a walk afterward.

Getting good quality and quantity sleep is also vital to consolidating and preserving memories. According to the National Institutes of Health, it appears that the deep stages of sleep help stabilize memories in the brain, while the more active REM sleep plays a role in linking related memories together. It’s worth noting that the NIH reports that by our late 30s, these deep stages of sleep start to decline, which has been linked to memory impairment.

The findings were published in the March 28, 2024 issue of the journal Science.

MBJ

Wendy Burt-Thomas writes about the brain, mental health and parenting.

Check out the original research:

https://www.science.org/doi/10.1126/science.adk8261

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