The old dogma that the adult human brain cannot generate new neurons was overthrown almost 10 years ago, but a question persists: do those new neurons do any good?
Only half the newborn neurons managed to take their place in existing brain circuits "when the mice lived in bare, boring cages. But when the mice lived in larger cages with running wheels, colored tunnels and playmates, the percentage of new neurons that slid into (and presumably strengthened) existing brain networks rose to 80 percent. That brings us full circle to the 2006 results on the cognitive benefits of aging: aerobic exercise not only boosts the rate at which the human brain makes new neurons, but also (in mice) makes more of them find a home that should be of benefit to the brain. Yet more proof that exercising the body can rejuvenate the mind.