Dr. Carl Cotman and his colleagues found that three weeks of wheel-running resulted in altered activity in rat brains, with increased expression of some genes and decreased expression of others. Many of the genes are responsible for helping the brain respond to stress, learn from experience, and resist brain insults, among other vital functions.

"Studies have indicated the benefits of exercise in preventing Alzheimer's disease, but none have shown how--and why--exercise might help the brain prevent the cell degradation that can lead to the disease," Cotman said. "Our studies demonstrate for the first time a connection between the genes that control growth hormones and other important molecules and the genes' ability to be stimulated by exercise. We think this may show us a way to determine how much and what types of exercise may help reduce the risk of cognitive impairment and perhaps Alzheimer's disease."

Alzheimer's disease affects more than four million Americans. Although researchers are looking at a wide range of options for treating and preventing the disease, they have only recently have looked at exercise as a possible prevention, according to the current article.

Using sophisticated DNA microarray, or gene chip, techniques, the researchers found that after three weeks of running on their cage wheels, rats had altered gene expression in the hippocampus. These broad changes in gene expression could improve the ability of the hippocampus to respond to outside influences, enabling the brain to be more adaptable to changing circumstances.

"We were surprised to find the concentration of activity in the hippocampus. We presumed that exercise principally would affect motor areas and not areas of higher function in the brain," Nicole Berchtold, a coauthor, said. "We also found a wide variety in the types of genes that were affected, indicating that exercise is a powerful regulator of brain activity."

Other researchers' work has shown that learning, a high-level brain activity, can affect the productivity of a wide variety of genes, including the gene for brain-derived neurotrophic factor and the genes encoding growth factors that stimulate growth of new neurons. Studies also have shown that running increases the growth factor levels in rat brains and improves the rats' learning ability in mazes.

The researchers are now looking at the complex interactions of the various genes in the hippocampus that appear to be controlled by exercise, in search of more evidence of how physical activity can affect brain functions during the aging process and might play a role in preventing Alzheimer's disease.