Brain+and+Exercise+-+3

Taken from [] New York Times, April 18, 2012 How Exercise Could Lead to a Better Brain

But it was the ineffable effect that exercise had on the functioning of the newly formed neurons that was most startling. Brain cells can improve intellect only if they join the existing neural network, and many do not, instead rattling aimlessly around in the brain for a while before dying.

One way to pull neurons into the network, however, is to learn something. In a 2007 study, new brain cells in mice became looped into the animals’ neural networks if the mice learned to navigate a water maze, a task that is cognitively but not physically taxing. But these brain cells were very limited in what they could do. When the researchers studied brain activity afterward, they found that the newly wired cells fired only when the animals navigated the maze again, not when they practiced other cognitive tasks. The learning encoded in those cells did not transfer to other types of rodent thinking.

Exercise, on the other hand, seems to make neurons nimble. When researchers in a separate study had mice run, the animals’ brains readily wired many new neurons into the neural network. But those neurons didn’t fire later only during running. They also lighted up when the animals practiced cognitive skills, like exploring unfamiliar environments. In the mice, running, unlike learning, had created brain cells that could multitask.

Just how exercise remakes minds on a molecular level is not yet fully understood, but research suggests that exercise prompts increases in something called brain-derived neurotropic factor, or B.D.N.F., a substance that strengthens cells and axons, fortifies the connections among neurons and sparks neurogenesis. Scientists can’t directly study similar effects in human brains, but they have found that after workouts, most people display higher B.D.N.F. levels in their bloodstreams.

Few if any researchers think that more B.D.N.F. explains all of the brain changes associated with exercise. The full process almost certainly involves multiple complex biochemical and genetic cascades. A recent study of the brains of elderly mice, for instance, found 117 genes that were expressed differently in the brains of animals that began a program of running, compared with those that remained sedentary, and the scientists were looking at only a small portion of the many genes that might be expressed differently in the brain by exercise.