A NY Times commentary on using imaging devices that show what occurs in the brain during meditation: The Monk in the Lab.
“The Dalai Lama’s belief that humans can curb dangerous impulses is based not only on spiritual practice and Buddhist teachings, but also on the work of scientists… the emergence of positive emotions may be due to this: Mindfulness meditation strengthens the neurological circuits that calm a part of the brain that acts as a trigger for fear and anger.”