There's an odd misconception that's held sway for about as long as anyone can remember, that learning is for kids.

If you don't learn a second language by the time you're 12, forget about it. Didn't learn to do a cartwheel when you were a spritely pre-adolescent? Don't expect to learn to do one now. You're too old. You might hurt yourself. It would be undignified. People will laugh at you. You'll fall on your face. Why bother at this point?

Well, to all of this, Lawrence Katz says, Bosh! Katz, a professor of neurobiology at Duke University Medical Center and co-author of Keep Your Brain Alive, makes a convincing argument that the more you learn, the better you learn.

"[Children's] brain cells are still growing, adding new connections, until about age 18 or so," explains Katz. "When you're older there's still some of this plasticity left, but you need to rely on different brain pathways."

By the time a person reaches adulthood, some of the brain's "wires" are permanently in use for other purposes. But there are always extra neural pathways that can be pressed into service. By doing what Katz calls neurobics, we can activate them.

Neurobics can involve any sort of new activity — from learning a new language to brushing your teeth with your left hand to trying to walk around your house with your eyes closed. Things involving as many of the senses as possible are optimal for nourishing our brains, says Katz. Activities that also involve interactions with other people are even better.