This ability to change the brain's wiring, to grow new neural connections, has been demonstrated in experiments such as one conducted by Doctors Avi Karni and Leslie Underleider at the National Institutes of Mental Health. In that experiment, the researchers had subjects perform a simple motor task, a finger-tapping exercise, and identified the parts of the brain involved in the task by taking a MRI brain scan. The subjects then practiced the finger exercise daily for four weeks, gradually becoming more efficient and quicker at it. At the end of the four-week period, the brain scan was repeated and showed that the area of the brain involved in the task had expanded; this indicated that the regular practice and repetition of the task had recruited new nerve cells and changed the neural connections that had originally been involved in the task.

— Dalai Lama

from The Art of Happiness