Heard about this on the Today Show this morning. This is from a Newsweek article ("Can Exercise Make You Smarter?" by Mary Carmichael) linked to the Today Show site:
The process starts in the muscles. Every time a bicep or quad contracts and releases, it sends out chemicals, including a protein called IGF-1 that travels through the bloodstream, across the blood-brain barrier and into the brain itself. There, IGF-1 takes on the role of foreman in the body's neurotransmitter factory. It issues orders to ramp up production of several chemicals, including one called brain-derived neurotrophic factor, or BDNF. Ratey, author of the upcoming book "Spark: The Revolutionary New Science of Exercise and the Brain," calls this molecule "Miracle-Gro for the brain." It fuels almost all the activities that lead to higher thought.
With regular exercise, the body builds up its levels of BDNF, and the brain's nerve cells start to branch out, join together and communicate with each other in new ways. . . .
Most people maintain fairly constant levels of BDNF in adulthood. But as they age, their individual neurons slowly start to die off. Until the mid-'90s, scientists thought the loss was permanent—that the brain couldn't make new nerve cells to replace the dead ones. But animal studies over the last decade have overturned that assumption, showing that "neurogenesis" in some parts of the brain can be induced easily with exercise. Last week's study, published in the Proceedings of the National Academy of Sciences, extended that principle to humans for the first time. . . .
In Small and Gage's experiment, the new neurons created by exercise cropped up in only one place: the dentate gyrus of the hippocampus, an area that controls learning and memory. This region, tucked under the temporal lobes, helps the brain match names to faces—one of the first skills to erode as we age. Fortunately, the hippocampus is especially responsive to BDNF's effects, and exercise seems to restore it to a healthier, "younger" state. "It's not just a matter of slowing down the aging process," says Arthur Kramer, a psychologist at the University of Illinois. "It's a matter of reversing it." Kramer's work also has implications for the frontal lobes, the seat of "executive functioning"—a type of higher thought that entails decision-making, multitasking and planning ahead. With scanning technology, he has found that exercise causes the frontal lobes to increase in size. . . .