Thousands of new cells are generated in the adult brain every day, particularly in the hippocampus, a structure involved in learning and memory.
Within a couple of weeks, most of those newborn neurons will die, unless the animal is challenged to learn something new. Learning—especially that involving a great deal of effort—can keep these new neurons alive.
Although the neurons do not seem to be necessary for most types of learning, they may play a role in predicting the future based on past experience. Enhancing neurogenesis might therefore help slow cognitive decline and keep healthy brains fit.
If you watch TV, read magazines or surf the Web, you have probably encountered advertisements urging you to exercise your mind. Various brain fitness programs encourage people to stay mentally limber by giving their brain a daily workout—doing everything from memorizing lists and solving puzzles to estimating the number of trees in Central Park.
It sounds a bit gimmicky, but such programs may have a real basis in neurobiology. Recent work, albeit mostly in rats, indicates that learning enhances the survival of new neurons in the adult brain. And the more engaging and challenging the problem, the greater the number of neurons that stick around. These neurons are then presumably available to aid in situations that tax the mind. It seems, then, that a mental workout can buff up the brain, much as physical exercise builds up the body.