Your Brain: The Missing Manual

Mental Fitness

You've now completed your first tour of the brain. Although you don't yet know all the reasons for the peculiar behavior of the planet's dominant species, you now have some of the tools that you can use to start asking the right questions. This makes it a good time to take a step back and change focus from low-level biology to more general guidelines. In this final section, you'll consider how you can keep your mental machine running in tip-top shape through the decades.

First, it's important to realize that the solution isn't to grow a bigger brain. After birth, it's rare for new neurons to appear in the brain. In fact, the story of the brain's development (which is told in Chapter 10) is largely the story of neurons and synapses dying off in waves as your body lumbers into old age. But don't panic yet. There's good reason to think that the loss of a few million neurons over the years is no big deal. In fact, it just might be part of the brain's natural housekeeping.

Rather than count the number of neurons in your head, it's more important to take note of the connections between them. As you've already learned, neurons are constantly being rewired. In healthy brains, the ratio of synapses to neurons grows as the number of neurons declines. In other words, leaner brains can become more efficient to compensate for their loss of neurons.

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.

  Tip

  There's no magic brain-honing activity. But 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.

  Note

  Don't think you can hone your brain with all-night Sudoku marathons. After the first 100 boards, your brain will have adapted itself to the patterns and strategies of the game, and will be able to polish off a board with far less neural work. On the one hand, this is a welcome development—after all, smart people use less activity for things they're good at. However, if your goal is to keep your brain strong, repeating the same type of challenge over and over again is no different than training with baby weights. For the maximum benefit, do something difficult and do something different.

• 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.)

• Give your brain good food and rest. Don't forget food and sleep. You'll learn all you need to know about brain-healthy eating and sleeping in the next two chapters.

Fun Facts: Using 100 Percent of Your Brain

You may have heard the pernicious rumor that humans use a mere 10 percent of the brain's capacity. Not only is this statement utter hogwash, no one's quite sure who to blame for it. Although there are cases where people have done remarkably well after suffering damage to large portions of their brain (particularly if they were young when the injury happened), you'd be ill-advised to give up even a single square inch of your own brain tissue.

As you'll discover in Chapter 2, the brain is the greediest, most resource-sucking of human organs. Put simply, the human body would never pay the high price of keeping the brain online unless every single neuron increased its chance of survival.