Physical Exercise Stimulates Stem Cells to Create New Brain Cells

Proceedings of the National Academy of Sciences, July 20, 2008

It has always been understood, at least intuitively if not scientifically, that physical exercise is important for proper health, mentally as well as physically. Indeed, a number of previous studies have indicated that people who engage in regular physical exercise score higher on memory tests than people who do not exercise. Now, researchers at Columbia University have shed some light on the specific mechanisms that are at work in the mental benefits that result from physical exercise.

Physical exercise targets a region within the hippocampus that is known as the dentate gyrus, a specialized region of the brain which is involved in memory, among other neurological processes. When the neurons of the dentate gyrus begin to atrophy over the years, the person is said to suffer age-related memory decline. Conversely, the growth of new neurons within the dentate gyrus will prevent memory decline - and this is exactly what happens as a result of physical exercise. Using MRI (magnetic resonance imaging), the researchers at Columbia University have now revealed that neurogenesis (the growth of new neurons) is stimulated in the dentate gyrus region immediately following physical exercise. These new nerve cells provide protection against the loss of memory with age.

In the past, prior to MRI technology, neurogenesis was observable only via postmortem examination, from which it was found that age-related memory decline typically begins around 30 years of age. However, the onset of memory decline was associated with this age only because this has traditionally been the stage of life at which people tend to become more habitually sedentary in their lifestyles, and less inclined toward serious physical exercise. By contrast, by prolonging regular physical exercise throughout life, neurogenesis in the dentate gyrus can continue up to any age. According to Scott Small, M.D., associate professor of neurology at Columbia University Medical Center, a research scholar at the Columbia University Taub Institute for Research on Alzheimer's Disease and the Aging Brain, and the principal investigator of the study, "I, like many physicians, already encourage my patients to get active and this adds yet another reason to the long list of reasons why exercise is good for overall health. Our next step is to identify the exercise regimen that is most beneficial to improve cognition and reduce normal memory loss, so that physicians may be able to prescribe specific types of exercise to improve memory."

The Taub Institute for Research on Alzheimer's Disease and the Aging Brain at Columbia University Medical Center is focused on the prevention and cure of Alzheimer's disease, Parkinson's disease and other age-related brain diseases. Fred Gage, Ph.D., of the Salk Institute in California, and a co-investigator in the study, had previously demonstrated in mice that exercise stimulates neurogenesis in the dentate gyrus, but this is the first concrete evidence of such exercise-related neurogenesis in the dentate gyrus of humans.