The Link Between Exercise and Memory (and Sleep?)

New research shows exercise optimizes the brain for memory consolidation.

Posted Jul 17, 2018

 iStock/Uberimages
Exercise improves connectivity in the brain and that boosts memory.
Source: iStock/Uberimages

Exercise is good for the brain. Your regular jog or spin class benefits memory and executive function. If you do it three or four times a week, exercise also improves your motor skills—anything requiring movement and muscles. Previous research has shown that the timing of the exercise affects how well it helps lay down memories

But no one knew very much about why this should be so. Now, a new study shows for the first time how exercise changes the brain in ways that might explain why it’s helpful for memory consolidation. “Your brain becomes more efficient,” says Marc Roig, a neuroscientist and physical therapist at McGill University in Montreal who is the senior author on the paper. What’s more, says Roig, the results suggest that a good night’s sleep could an important part of the process.

The paper, published in NeuroImage, and co-authored by Fabien Dal Maso, Bennet Desormeau and Marie-Hélène Boudrias, focuses on motor learning and memory. Roig and his colleagues work with rehabilitation patients, especially those who’ve suffered a stroke. “The idea is to try to use exercise coupled with motor learning to improve the retention of motor skills in patients,” Roig says. But their findings could apply to sports training as well. And since exercise has been found to improve other kinds of memory, such as visual or verbal memory, the study may have wider implications.

In the first part of the study, Roig and his colleagues confirmed something they’ve found before. A bout of acute exercise immediately after practicing a motor task improved retention 24 hours later. “It seems like you open a window of brain plasticity and that helps what you learn to be consolidated more effectively,” says Roig.

To demonstrate this, they first asked two groups of young adults to learn what was essentially a muscular video game. The participants manipulated a joystick capable of measuring the force of their grip and they had to move a cursor on a computer screen, putting it within specific targets. Immediately after the task, one group exercised hard on a stationary bicycle for fifteen minutes. The other group didn’t exercise. They just sat on the bike without pedaling. 

To investigate brain activity, the researchers added a simple motor task very like the muscular movements that the game had required. After either exercising or not, the volunteers had to simply grab a joystick and apply a certain amount of force. While they did that, the researchers measured the electrical activity in their brains over the following two hours. “The two hours after are critical for the consolidation of a memory,” Roig says. “In [that time], your brain will decide if it wants to retain this information or not.”

Finally, they asked everyone to return 8 hours and 24 hours later to play the game again. “This is just to measure memory,” Roig says. The entire exercise is similar to being asked to memorize a paragraph and then trying to repeat the paragraph eight and 24 hours later to see how many words you remember. “That’s exactly the same, but in this case it’s a motor task, it’s not a paragraph,” Roig explains.

“What we found was that when they were doing the simpler motor task the brain activity was much lower and the connectivity between different brain areas was much higher [in the exercise group],” Roig says. Specifically, they found an increase in connectivity both within and between hemispheres of the brain and it was especially prevalent in motor sensory areas, which are in charge of the execution and planning of movements. In addition, “this lower activity and higher connectivity were correlated with how well they remembered the motor task.” 

Roig and his colleague suspect this means that exercise streamlines the work the brain has to do to remember something. “What exercise seems to be doing is to reduce the demands of the brain, so memories can be consolidated more efficiently because there is much better connectivity of the different parts of the brain.”

Putting exercise immediately before motor learning can work, too, by the way. But done that way, the exercise must be more moderate or there is a risk of tiring people out so much that they can’t attend to the learning. When Roig has separated the motor learning and exercise by two hours or more, the beneficial effects on retention disappear.  

The possible importance of sleep emerges in the last phase of the study. When participants return and play the game eight hours later, the exercise group doesn’t seem to be any better than the control group. In fact, no one is very good. That’s a finding that has shown up in Roig’s previous studies as well. But the next day, 24 hours after the initial learning took place, the group that exercised shows significantly more memory of the skill than the control group. “My hypothesis is there is an interaction between exercise and sleep,” Roig says. “We know that sleep is relevant for memory consolidation and we know that exercise can improve mental consolidation, but what we’re seeing in my studies is that unless you sleep, you don’t benefit from the effects of exercise.”

What Roig calls “the triangle” of exercise, sleep, and memory is relatively unexplored. But not for long. He has just begun a new set of studies that will include monitoring participants while they sleep. “I think maybe exercise changes brain architecture to improve memory, but unless you sleep you don’t see this improvement.” 

He won’t be able to say for sure until these next studies are complete, but the next time you want to learn a new skill, why not plan on some exercise afterwards and a good night’s sleep? It couldn’t hurt.

Copyright: Lydia Denworth 2018.

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