Although studies have shown a link between exercise and memory, it hasn’t been clear how they are connected. But now, researchers at the University of Illinois believe they have identified a key brain tissue structure that may be responsible.

The scientists believe the microstructure of the brain’s hippocampus, a region involved in memory processes, plays a role in the link between fitness and memory. Particpants who did better on a memory test also did better on a cardiovascular fitness test; additionally, people who had better fitness scores also had more elastic tissue in their hippocampus.

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The study, published in the journal NeuroImage, involved 51 healthy young adults. Researchers used a specialized brain scan technique to analyze the structural integrity of the hippocampus in the participants’ brains. They then paralleled it with their results on fitness and memory tests. Their findings revealed viscoelasticity, a measure of structural integrity in brain tissue, correlated with the test results.

Viscoelasticity is a property in which the tissue is both elastic, like a firm foam-mattress, and viscous, like a memory-foam mattress, study author Curtis Johnson explained in a news release. The researchers found that a more elastic hippocampus, rather than viscous one, correlated with better fitness and memory.

“Using a new tool to examine the integrity of the hippocampus in healthy young adults could tell us more about how this region functions and how to predict decline for early intervention,” said study author Aron Barbey. “By the time we look at diseases states, it’s often too late.”

Barbey’s study is unique because prior research has primarily focused on the size of the hippocampus, rather than its structure. To better understand the structure, all of the participant’s underwent a usual MRI scan, but with an added component - a vibrating pillow placed under their head. The pillow, which emitted very light vibrations, was key to analyzing the integrity of the hippocampus.

“It’s a lot like sending ripples through a still pond - if there’s some large thing like a bounder under the surface, the ripples are going to displace around it,” said researcher Hillary Schwarb. “We are sending waves through the brain and reconstructing the displacements into a map we can look at and measure.”

The authors found that more often than not, those who performed better on the fitness test, also did better on the memory task, which confirmed their past findings. Additional insight from this new study showed those who had better cardiovascular health had more elastic tissue in the hippocampus.

“An elastic tissue is like a firm foam mattress pad that pops right back up after you get up,” said study co-author Curtis Johnson. “When the hippocampus is more viscous, memory is worse. A viscous hippocampus is like a memory-foam mattress that holds its shape even after you get up.”

The study results also show that the emerging, non-invasive technique perfomed, called magnetic resonance elastography, is “a useful tool for understanding microstructure, and that microstructure is important to cognition” said Schwarb.

See also: Workout For The Human Brain: Can Exercise Boost Memory For The Elderly?

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