Brain cells communicate with one another via tiny branchlike cells called dendrites. As we age, our ability to form dendrites declines, which is why our memory wanes and we have more difficulty learning new tasks. Dendrite growth peaks before adolescence. This is one of the reasons that children pick up languages, musical instruments, and other skills so readily while we adults struggle with them. If your child or grandchild has ever tried to teach you how to play a video game, you know what I am talking about. Children's brains make connections faster. After puberty, the formation of new dendrites slows down, and at that point connections that are used frequently become permanent while those that are underutilized are lost. Through the years there is a constant brain drain, resulting in fewer and fewer new dendrites.

When I was in medical school, we were taught that the adult brain was fully formed and that it could not grow new cells. Now we know better. We have learned that the brain is extremely resilient, even in adulthood, and that it has an amazing capacity to restore itself if it is given the proper stimulation. We have learned that if we use our brain by challenging ourselves mentally, we can build new nerve connections and strengthen neuron pathways. The result is increased brain power and a more youthful functioning brain. Animals have demonstrated that intellectual challenges encourage neurons to branch out and create new connections, and there is compelling evidence that the same is true for humans.

You may be surprised that nuns are remarkable not only because they live considerably longer than the general population but they also suffer significantly less dementia and Alzheimer's disease, even in their older years. They live healthy lives and have a strong social support structure, but beyond that, they have something which is even more important, an ethic of intellectual stimulation. They make it a point to read, play word games, do puzzles, work on their vocabularies, and continue to contribute to the convent in meaningful ways throughout their lives. Even more fascinating, brain scans show that the better educated nuns are those who teach, study, and continue to learn have significantly more cortex, the area of the brain associated with language and reasoning, and more dendrites than the nuns whose work is less mentally stimulating, such as cooking and cleaning.

The exercise analogy is inevitable. Use it or lose it. Yes, optimal nutrition is vital, but even if you eat the best of diets and have a broad-spectrum nutritional supplement program, your cardiovascular and muscular fitness will suffer without exercise. The same is true of your brain and cognitive fitness.