Dec. 7, 1999 (Atlanta) -- A mouse study published in a recent issue of Proceedings of the National Academy of Sciences suggests that running improves learning and memory. The study researchers from the Howard Hughes Medical Institute also found that exercise stimulates the growth of new brain cells in mice.
The study compared the memory of a group of mice made to exercise on a running wheel with mice who were not exercised regularly. Memory was determined by the speed at which the mice located a hidden platform in a water maze, used previously as a refuge to avoid swimming. Researchers also compared signaling processes of nerve cells by examining brain tissue.
Mice that exercised regularly found the dock significantly faster and had more than twice the number of new brain cells in the hippocampus, the primary location in the brain for memory formation and spatial learning. They also had stronger cellular connections, known as synapses, critical for information flow and memory storage.
"We've always thought that brain cells didn't regenerate in adult mammals," Terrence Sejnowski, PhD, the chief HHMI investigator at the Salk Institute for Biological Studies in La Jolla, Calif., tells WebMD. "But now we have evidence of neurogenesis, and it appears to be stimulated by exercise." Neurogenesis is the formation of new nerve cells.
This new link between exercise and learning was recently the focus of a national conference for scientists and educators. John Ratey, MD, reported at the conference that exercise also has a positive effect on brain chemistry that regulates mood. "Studies show that exercise may be a better approach for some than antidepressant drug therapy, and doctors are taking notice," he tells WebMD. "In fact, one study of cancer patients showed a 40% decrease in depression after exercise was prescribed." Ratey is a clinical associate professor of psychiatry at Harvard University.
Another presenter, Elizabeth Gould, PhD, a neurobiologist at Princeton University, discussed her own recent finding that female sex hormones stimulate the growth of new brain cells. Although Gould's research is further evidence that the brain undergoes changes throughout the life span, she urged caution in response to these animal studies. Physicians, however, are already aware of estrogen's positive effect on memory.
"We've known for a while that estrogen replacement therapy, used to prevent osteoporosis and cardiovascular disease in postmenopausal women, seems to enhance memory," says David Lowenthal, MD, the director of geriatric research at the VA Medical Center in Gainesville, Fla., and professor of medicine at the University of Florida. "In fact, use of estrogen in the prevention of Alzheimer's disease is currently being explored in clinical trials."
Lowenthal's own research is taking an entirely different direction. "As an exercise physiologist and gerontologist, I'm most excited about the effects of aerobic training on symptoms of [learning and memory] disorders. When the study gets underway, we're likely to see improvements in both sleep quality and attention span."
Clinical researchers are also exploring the effects of brain cell growth factors, or neurotropins, in Parkinson's disease, says Sejnowski. "There are a lot of possible links to explore. But today, there is absolutely no doubt that exercise helps maintain physical health and mental sharpness," he says. "Now that the data is in, I'm gonna leave for a long brisk walk whenever I lose my glasses!"
- A new study on mice shows that exercise stimulates the growth of new brain cells and improves memory.
- Exercise can also improve mood, according to study on cancer patients who were able to reduce depression by 40% by exercising.
- Other findings show that the female hormone estrogen can encourage the formation of new brain cells.