Thanks to MindHacks for the link to a good Washington Post article, “Pumping Neurons”.
A couple of quotes:
Recent research shows that the brain remains plastic, or basically trainable, throughout life. In a study published in the Journal of the American Medical Association in 2002, significant percentages of the 2,802 participants age 65 and older who trained for five weeks for about 2 1/2 hours per week improved their memory, reasoning and information-processing speed.
When we learn, we create physical changes inside our heads. By practicing a skill, we repeatedly stimulate the same area of the brain, which strengthens existing neural connections and creates new ones. Over time, we can become more cognitively efficient, using fewer neurons to do the same job. And the more often we fire up certain mental circuits, the easier it is to get them going again.