Use it or lose it. We know that about our bodies.
But a growing line of research now shows that the same is true for our brains. How we live, and what we do, can actually have a profound impact on the physical structure of the brain.
If we are what we eat, as the old saying goes, we may also be what we think. Or how we think, as well as how much we think.
One treatment for some of our mental ills may well lie in the practice of meditation, an awareness of sensations, feelings and state of mind.
The latest evidence comes from an impressive group of researchers from some of the leading institutions in the world who have found that a serious effort at meditation can physically change the brain, leading to reduced stress, better mental focus, and possibly fewer effects from aging.
"The structure of the brain is very complex and it is constantly changing," says Sara Lazar, a psychiatrist and research scientist at Massachusetts General Hospital and Harvard University. "It is well documented that around the age of 20 to 25 the whole front of the brain starts to get thinner with age, and other parts of the brain continue to grow, and all sorts of things are happening, all of the time."
Diet, education, aging and how we use our time all have a big impact on changes in the structure of the brain, she notes.
Lazar, who is obsessed with how the human brain functions, took up meditation nearly a decade ago, partly because she had heard reports of how it can help keep the brain in tune, but she wasn't sure if it was true.
Today, she has very little doubt.
"The difference is like night and day," she says. It shows up in a reduction in stress, being able to remain focused and dealing with "difficult situations," she says.
And now, she has reason to believe it changed her brain physically, in ways that are consistent with improvement in all those areas.
Lazar led a team of researchers who used that fantastic new tool, magnetic resonance imaging, to literally peer into the brains of 20 subjects who regularly practice meditation, and 15 who don't. They found that the regions of the brain that are associated with attention, sensory processing and stimulation where "thicker" in the brains of the meditators than in the others. The evidence also suggests that meditation may help ward off the thinning of those regions of the brain caused by aging.
What's interesting about the study is these meditators aren't a bunch of monks. Previous research had already shown that Buddhist monks in Tibet who were devoted to meditation and spent many hours every day practicing it had experienced changes in mental processing.
But Lazar and her colleagues wanted to know if this only worked for those who are totally immersed in the process, or if a few hours a week do the same thing.
Participants in the study meditated only an average of about 40 minutes a day. Some had done it for only a year or so. Others had done it for decades.
The structural changes were most prominent among those who have meditated for longer periods, and it was especially strong for those who showed evidence of having mastered the art.
The participants in the study were "people who practice mindfulness-based meditation, paying attention to breathing and internal processes," says Jeremy Gray, a cognitive psychologist at Yale and a co-author of the study, which appeared in a November issue of NeuroReport.