Walking can help the brain work better, study says

Exercise can refresh and renew white brain mass, potentially improving memory and thinking skills as we age, a new study on walking, dancing and brain health has revealed.

The study shows that white matter, which connects and sustains our brain cells, remodels when people become more physically active. In the case of people who remain sedentary, the white mass tends to shrink and wear out.

The findings underscore the dynamism of the brain and how it constantly changes, for better or worse, in response to how we live and move.

The idea that the adult brain can be malleable is a more or less recent discovery, in scientific terms.

Until the late 1990s, most researchers considered the human brain to be physically fixed and inflexible from early childhood onwards. The common idea was that we are born with most of the brain cells we will ever have, and we cannot produce more. In this scenario, the structure and function of the brain would only weaken with age.

But science has, thankfully, moved forward and reconsidered this grim prognosis. Complex studies using specialized pigments to identify newborn cells have indicated that some parts of the brain create neurons even into late adulthood, in a process known as neurogenesis.

Later studies found that physical exercise amplifies neurogenesis. When rodents run, for example, they generate three to four times more new brain cells than sedentary animals do.

And among humans, starting a regular exercise program leads to increased brain volume. Essentially, the study demonstrates that the human brain retains its plasticity throughout life, changing as we change, including in response to how we exercise.

But most past studies of brain plasticity have focused on gray matter, which contains the famous little gray cells, or neurons, that enable and create thoughts and memories.

The white matter, which forms the “wiring” of the brain, has been less researched. Comprised primarily of nerve fibers encased in fat and known as axons, white matter connects neurons and is essential for brain health. But it can be fragile, thin and start to show small lesions as we get older.

These dilapidations may be precursors to cognitive decline. A worrying fact is the white matter has also been seen as being relatively static, endowed with little plasticity or ability to adapt to changes in our lives.

But Agnieszka Burzynska, a professor of neuroscience and human development at Colorado State University in Fort Collins, thought science might be underestimating white matter.

“She has been seen as an ugly, despised half-sister” of the gray matter, she said, being ignored and misjudged. Burzynska thought it likely that the white mass had as much plasticity as the gray one and was capable of reshaping itself, especially if people started to move.

So for the new study, which was published online in June in NeuroImage, she, her graduate student Andrea Mendez Colmenares and other colleagues set out to reform some people’s white matter.

They began by gathering nearly 250 elderly men and women who were sedentary but otherwise healthy. They tested the aerobic fitness and cognitive abilities of these volunteers in the laboratory and also measured the health and function of their white matter using a sophisticated form of MRI.

They then divided the volunteers into groups, one of which began a supervised program of stretching and balance training three times a week to serve as an active control. Another group began taking brisk walks together three times a week, for about 40 minutes each time. And the final group started dancing, meeting three times a week to learn and practice line dancing and group choreography.

All groups trained for six months and then returned to the lab to repeat the tests done at the beginning of the study.

Scientists found that the bodies and brains of many of the participants had changed. The walkers and dancers had increased their aerobic fitness, as predicted. More importantly, his white mass looked renewed. In the new MRIs, nerve fibers in certain parts of their brains appeared larger and any lesions had shrunk.

These desirable changes were more prevalent among hikers, who were also doing better on memory tests. The same did not happen with the dancers, in general.

Meanwhile, the white matter health of the non-aerobic control group members had declined after six months, with greater thinning, more axonal wear and tear and lower cognitive scores.

These findings hold great promise for those who exercise, said Dr. Burzynska. They tell us that white matter remains plastic and active no matter how old we are, and that a few brisk walks a week can be enough to polish the tissue and slow or stave off memory decline.

Of course, the brain changes were subtle and somewhat inconsistent. Burzynska and her colleagues had predicted, for example, that dancing would generate more white matter changes and cognitive improvements than walking, since dancing involves more learning and training. But walking proved more potent, suggesting that aerobic exercise itself is most important to white matter health.

“The dancers spent time in each session watching the instructors, not moving too much,” Burzynska said. “That must have affected your results.”

Participants in the study were over 60, were inactive, and had only exercised for six months. It remains unclear whether the brains of younger, fitter people would also benefit, or whether longer-term aerobic exercise could result in greater improvements in memory and thinking. But for now, says Burzynska, the results already constitute “a compelling argument for people to get up and move.” For the sake of your white mass.

Translation by Clara Allain