These past studies of brain plasticity generally focused on gray matter, though, which contains the celebrated little gray cells, or neurons, that permit and create thoughts and memories. Research on white matter, also known as the wiring of our brains, is much less common. White matter, made mostly from fat-wrapped nerve cells known as axons and essential for brain function, is composed primarily of white matter. It can also be fragile, and it can thinning and develop small lesions with age. This could lead to cognitive impairment. It has also been considered to be relatively static with limited plasticity and 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, suspected that science was underestimating white matter. She said that gray matter had been “like the ugly, neglected stepsister” of white matter. This was something she has ignored and wrongly judged. She believed that white matter could be refashioned, even if it had more plasticity than its gray counterpart.
Andrea Mendez Colmenares, Andrea’s graduate student, and others set out to alter white matter. They began by gathering 250 older men, women and children who were healthy but not sedentary. At the lab, they tested these volunteers’ current aerobic fitness and cognitive skills and also measured the health and function of their white matter, using a sophisticated form of M.R.I. brain scan.
The volunteers were divided into groups and one group started a supervised program to strengthen their balance and stretch three times a weeks. Another started walking together three times a week, briskly, for about 40 minutes. And the final group took up dancing, meeting three times a week to learn and practice line dances and group choreography. All of the groups trained for six months, then returned to the lab to repeat the tests from the study’s start.
The scientists discovered that many people’s brains and bodies had changed. As expected the walkers and dancers were much more aerobically fit. Their white matter appeared to be renewed, which was even more important. New scans revealed that nerve fibers in some brains were larger than before, and that any tissue lesions had decreased. These desirable changes were most prominent in walkers, who now perform better on memory tests. The dancers didn’t.