Basic Tips for Mental Fitness from Your Brain: The Missing Manual

So what can you do to keep your brain in its best working form? There may be no way to dodge bad genes, bad luck, injury, and disease, but studies of brain aging consistently identify a few characteristics in old-aged but nimble-brained people. Here are a few practical guidelines if you hope to become a quick-witted fast-talking 90-year-old cribbage shark:

• You are what you do. The brain is constantly rewiring the connections between your neurons, strengthening the ones you use and weakening the ones that you don't. In other words, when you spend a day munching Cheetos, watching American Idol reruns, and lamenting the tragedy of your life, you aren't just whiling away the time. You're also training your brain to be a better Cheetos-eater, TV watcher, and chronic worrier. Fall into this pattern for a few years, and your brain just won't look the same.

• Use it or lose it. The brain may not be a muscle, but there's good evidence that the human body doesn't waste effort maintaining mental hardware that you never use. Surprisingly, it seems that it's never too late to ramp up your thinking. Many studies suggest that suddenly giving your brain more to do, even late in life, can overcome recent brain decline and foster broad, long-term improvements. While there's no magic brain-honing activity, broad, integrative tasks like studying a new language, learning to play a musical instrument, changing jobs, writing a book, picking up a new hobby, and planning the perfect crime are all good prospects.

• Embrace something different. The brain craves novelty. The best way to keep your brain stimulated is to activate as much of it as often as you can. There's a fun side to this advice ("Indulge your curiosity!" "Engage strangers in long conversations!"), and a more challenging side ("Turn off the TV and learn differential calculus!"). The bottom line is that most of the time, the human body craves dull and easy stability. However, the brain thrives with constant challenges, tricky concepts, extreme concentration, and, well, work.

• Exercise the body to help the mind. Studies suggest the keenest old brains have owners who exercise regularly. The best bet seems to be modest aerobic exercise, such as a daily jog or brisk walk. It's unclear why this helps, although it could well be that exercise stimulates other body processes that benefit the brain.

• It wouldn't hurt to strum a tune. The popular media is filled with tantalizing studies suggesting that a bit of music listening or music making can boost test scores and cultivate a baby genius. The truth is that the human brain is unlikely to respond to a magic music pill. However, exposing your brain to as many different influences as possible is always a surefire way to promote its development. Learning music as a discipline--in other words, as something to read, play, or improvise--is likely to draw on regions of the brain that are left dormant through the rest of your day-to-day life. (That said, if you're already an accomplished musician, your brain has long-ago transformed the challenging problems of making music into deeply ingrained neural patterns that take little effort. As a result, you'll get more brain stimulation by taking up accounting.)