Why Do Aerobically Fit Children Have Better Math Skills?

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A new study from the Beckman Institute at the University of Illinois at Urbana-Champaign reveals that 9- and 10-year-old children who are aerobically fit tend to have significantly thinner gray matter in the cerebrum than their "low-fit" peers. Interestingly, thinning of the outermost layer of brain cells in the cerebrum is associated with better math skills, according to the researchers.

The August 2015 study, "The Role of Aerobic Fitness in Cortical Thickness and Mathematics Achievement in Preadolescent Children,” appears in the journal PLOS ONE.

Cerebrum (Latin for brain) in red.

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The new study finds a correlation—but not direct causation—between cardiorespiratory fitness and cortical gray matter thinning in the cerebrum. Thinning of gray matter is also known as "neural pruning," which is an important aspect of neuroplasticity during brain development and throughout a person's lifespan.

This study also offers the first direct evidence that fitness improves arithmetic performance on standardized tests by aiding the development of brain structures that contribute to mathematics achievement. Again, the scientists emphasize that they have identified a correlation, but more research is needed to identify a causal relationship.

Laura Chaddock-Heyman, led the research with fellow Beckman Institute for Science and Technology director Art Kramer and kinesiology and community health professor Charles Hillman. Previous studies have shown that gray-matter thinning is associated with better reasoning and thinking skills. In a press release, Chaddock-Heyman said:

Gray-matter loss during child development is part of healthy maturation. Gray-matter thinning is the sculpting of a fully formed, healthy brain. The theory is that the brain is pruning away unnecessary connections and strengthening useful connections.

We show, for the first time, that aerobic fitness may play a role in this cortical thinning. In particular, we find that higher-fit 9- and 10-year-olds show a decrease in gray-matter thickness in some areas known to change with development, specifically in the frontal, temporal and occipital lobes of the brain.

These results support and extend research on changes in cortical surface organization during child development. The new data suggests that individual differences in aerobic fitness may influence brain areas by significantly changing cortical thickness during development, and perhaps throughout a person's lifespan.

Gray Matter and White Matter Work Together to Optimize Brain Function

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Gray matter houses the neurons in specific brain regions. White matter creates communication lines between various brain regions. In 2014, Chaddock-Heyman et al found that higher levels of aerobic fitness in children is associated with improved white matter integrity. The team identified that exercise improves the microstructures of white matter in the brain. White matter integrity is linked to faster neural conduction between brain regions and superior cognitive performance.

In two separate 2014 studies—released within the same month—the Beckman researchers reported that physical activity improved the white matter integrity of physically fit children aged 9 to 10 and also in “low-fit” participants aged 60 to 78. I wrote about these findings in a Psychology Today blog post, "Why Is Physical Activity So Good for Your Brain?"

Based on the most recent findings on gray-matter thinning coupled with last year's findings about white matter integrity, I emailed Laura Chaddock-Heyman yesterday to ask her about a possible connection between all of these findings.

My question was: "Do you believe the healthy neural pruning of cortical gray matter and the improvement of white matter integrity are working together to improve cognitive function and math achievement in children who are more fit?" Chaddock-Heyman responded via email:

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Indeed, ‎it is likely a combination of many differences in the structure and function of the brains of higher fit and lower fit children that could lead to differences in cognitive and academic performance. Much of our MRI work provides clues as to why higher fit children may outperform their lower fit peers on cognitive and academic tests.

Higher fit children have larger structural brain volumes in the hippocampus and dorsal striatum, two subcortical regions critical for memory and learning (Chaddock et al., 2010a,b), as well as more efficient brain activation patterns (via functional magnetic resonance imaging [fMRI] and event-related potential [ERP] measures) during attentional and interference control tasks (Chaddock, Erickson et al., 2012; Chaddock-Heyman et al., 2013; Hillman, Buck, Themanson, Pontifex, & Castelli, 2009; Pontifex et al., 2011; Tomporowski, Davis, Miller, & Naglieri, 2008; Voss et al., 2011), relative to lower fit peers.

Higher fit children also show greater structural integrity (via fractional anisotropy, measured using diffusion tensor imaging) in white matter tracts that carry information throughout the brain (Chaddock-Heyman et al., 2014). The present study adds fitness differences in cortical thickness to this list.

Conclusion: Exercise and Physical Fitness May Improve Academic Performance

The latest groundbreaking discovery from the Beckman Institute enriches our understanding of childhood brain plasticity and suggests that improved math skills are linked to aerobic fitness. The correlation of aerobic fitness and academic performance highlights the importance of regular physical activity during and after school. In a press release, co-author Charles Hillman stated,

These findings arrive at an important time. Physical activity opportunities during the school day are being reduced or eliminated in response to mandates for increased academic time. Given that rates of physical inactivity are rising, there is an increased need to promote physical activity. Schools are the best institutions to implement such health behavior practices, due to the number of children they reach on a daily basis.

These findings provide additional evidence that increased aerobic fitness levels may enhance cognitive function and brain plasticity, with potentially significant outcomes related to a child's scholastic achievement.

Chaddock-Heyman, Hillman, and Kramer will continue to explore differences in the brains of higher fit and lower fit children during childhood development. They are currently seeking to identify causal relationships between aerobic fitness, changes in the structure and function of the brain, and improved academic performance.

Art Kramer concluded, "An important next step in this research is to establish a causal relationship between brain changes, changes in physical fitness and changes in cognition and school achievement—something we are currently doing with a longitudinal study of children participating in a physical activity training program."

I also asked Chaddock-Heyman if there were any plans to explore the role that the structure and function of the cerebellum (Latin for little brain) might be playing in the link between physical activity, aerobic fitness, and academic performance. She replied, "It would be interesting for future work to examine how the structure of the cerebellum predicts skills in and out of the classroom, too."

If you'd like to read more on this topic, check out my Psychology Today blog posts:

• "Why Does Physical Inactivity Drain Human Brain Power?"
• "Physically Fit Children Have Enhanced Brain Powers"
• "Want to Improve Your Cognitive Function? Go Climb a Tree!"
• "One More Reason to Unplug Your Television"
• "Why Does Aerobic Activity Improve Cognitive Function?"
• "Better Motor Skills Linked to Higher Academic Scores"
• "Scientists Discover Why Exercise Makes You Smarter"
• "Too Much Crystallized Thinking Lowers Fluid Intelligence"
• "Can Physical Activities Enhance Fluid Intelligence?"
• "Physical Activity Boosts Brain Power"
• "Childhood Poverty Has Detrimental Impacts on Brain Structure"
• "Why Do Rich Kids Have Higher Standardized Test Scores?"
• "How Does Physical Fitness Improve Your Brain Function?"

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