The question we are left with is, what should we do to stimulate our personal cognitive development, and when do we know it's working? When you do sit-ups, you expect to develop killer abs. We know that when we run or bike for an hour, we feel either exhausted or invigorated by an endorphin rush. But that wears off quickly. How do we know we are doing enough to help the brain muscle?
And if running is so good, what about sports that also involve more thinking, more teamwork, the kind of social interaction that psychologists have long linked with better mental health of the psychologic kind?
The answers will be a long time coming, but there are some theories, at least. "Social stimulus is often quite effective" in neurofunctioning, says Gage, who thinks other sports that involve social interaction may have advantages for neurogenesis, as long as they are aerobic.
"Scientists tend to use running or walking experimentally because they can isolate it and talk about it and say yes, independent of social interaction, independent of any learning experience, independent of any other variables, just exercise alone is adequate," he says. "It doesn't mean that there aren't many other ways that you can go to get there."
The bottom line is, until we know better, it is best to keep running, or start an exercise program that gets the blood pumping. It's good for mind, body and soul.
Running, biking and playing tennis get blood flowing to the brain, but sweating isn't the only way to get and stay smart, neuroscientists believe.
The mind needs to play internal games as well to stay sharp, says Dr. Amir Soas, of the Case Western Reserve University Medical School in Cleveland. "If there are areas in the brain that you totally don't use or that remain unused over a long period of time, they have a tendency to deteriorate like anything else in your body," he says.
The more complex the task, the more synapses are firing in more parts of the brain. Just as you would build new blood vessels in your quadriceps muscles in your legs, you need mind workouts to keep the network of blood vessels in the working parts of the brain growing and healthy. Research indicates this can even stave off Alzheimer's and Parkinson's diseases in people likely to develop those afflictions.
Activities like writing a short story, learning to play chess or a new language, or even doing a crossword puzzle involve more than one thing, using more of your brain, so a greater number of synapses are working simultaneously (see Mind Games: Creating New Brain Cells).