The term refers to the brain's recently discovered ability to change its structure and function, in particular by expanding or strengthening circuits that are used and by shrinking or weakening those that are rarely engaged. In its short history, the science of neuroplasticity has mostly documented brain changes that reflect physical experience and input from the outside world. In pianists who play many arpeggios, for instance, brain regions that control the index finger and middle finger become fused, apparently because when one finger hits a key in one of these fast-tempo movements, the other does so almost simultaneously, fooling the brain into thinking the two fingers are one. As a result of the fused brain regions, the pianist can no longer move those fingers independently of one another.

Lately, however, scientists have begun to wonder whether the brain can change in response to purely internal, mental signals. That's where the Buddhists come in. Their centuries-old tradition of meditation offers a real-life experiment in the power of those will-o'-the-wisps, thoughts, to alter the physical matter of the brain.