"We found that regions of the brain that are intimately involved in the control and regulation of attention, such as the prefrontal cortex, were more activated in the long-term practitioners," Davidson says.
A different picture emerged, however, from looking only at the most experienced meditators with at least 40,000 hours of experience. "There was a brief increase in activity as they start meditating, and then it came down to baseline, as if they were able to concentrate in an effortless way," says Davidson.
Effortless concentration is described in classic meditation texts, adds Davidson. "And we think this may be a neural reflection of that. These results illustrate one mechanism by which meditation may act in the brain."
While the subjects meditated inside the MRI, the researchers periodically blasted them with disturbing noises. Among the experienced meditators, the noise had less effect on the brain areas involved in emotion and decision-making than among novice meditators. Among meditators with more than 40,000 hours of lifetime practice, these areas were hardly affected at all.
"Most people, if they heard a baby screaming, would have some emotional response," Davidson says, but not the highly experienced meditators. "They do hear the sound, we can detect that in the auditory cortex, but they don't have the emotional reaction."
As Davidson notes, any comparison of average middle-aged Americans to people who have meditated daily for decades must try to associate the differences with meditation, and not lifestyle factors such as isolation or religious faith.
"This was a highly unusual group of people. Two-thirds of the experienced meditators were Tibetan monks, recruited with the help of the Dalai Lama, and they all had an extremely long history of formal practice."
For 15 years, Davidson has had a scientific relationship with the Dalai Lama, spiritual leader of Tibetan Buddhists, to investigate the effects of meditation.
Still, the correlation between more meditation experience and greater brain changes does suggest that the changes were caused by meditation.
"If it were simply lifestyle, we would not expect a very strong correlation with hours of practice," Davidson says.
Other evidence for the neurological benefits of meditation came from a study Davidson reported in May, which showed that three months of meditation training improved the ability to detect a brief visual signal that most people cannot detect. "That was a more definitive kind of evidence, because we were able to track the same people over time," he says.
Psychologists have long considered an adult's capacity to pay attention as relatively fixed, but Davidson says: "Attention can be trained, and in a way that is not fundamentally different than how physical exercise changes the body."
The attention circuits affected by meditation are also involved in attention deficit hyperactivity disorder, which Davidson describes as the most prevalent psychiatric diagnosis among children in our country.
"Our findings suggest that it may-I stress may-be possible to train attention in children with methods derived from these practices," he says.
Davidson says scientific studies of meditation are proving traditional beliefs about the mental benefits of meditation. Yet although meditation is often associated with monks living a life of simplicity, poverty, and prayer, "There is nothing fundamentally mysterious about these practices; they can be understood in hard-nosed western scientific terms."
And, he adds, a growing body of "hard-nosed neuroscience research" is attracting attention to the profound effects of meditation.
"This deserves serious scientific attention," he says. "It also explains why people spend time sitting on the meditation cushion, because of the effects on day-to-day life."
Davidson compares mental practice to physical exercise.
"We all know that if an individual works out on a regular basis, that can change cardiovascular health," he says. "In the same way, these data suggest that certain basic mechanisms of the mind, like attention, can also be 