Meditation has been used to help treat pain, addiction, anxiety disorders, and depression; but it was personal experience that prompted Judson Brewer, M.D., Ph.D., to study the neural mechanisms behind it.

Brewer, assistant professor of psychiatry and medical director of the Yale Therapeutic Neuroscience Clinic, began practicing meditation to deal with stress while a student at the Washington University School of Medicine. “I had seen that it was helpful for my life and that was why I went into psychiatry,” he said. During his residency he found that meditation helped addicts manage their cravings. But until recently scientists did not understand what brain mechanisms account for meditation’s beneficial effects.

In a study published online in November 2011 in the Proceedings of the National Academy of Sciences, Brewer and colleagues reported that the brains of experienced meditators—those who have been meditating for at least 10 years—showed decreased activity in the areas linked to attention lapses, anxiety, attention-deficit hyperactivity disorder, schizophrenia, autism, and plaque buildup in Alzheimer disease. This effect was seen regardless of the type of meditation practiced. The areas in question comprise the default mode network, which consists of the medial prefrontal and posterior cingulate cortices.

The team used functional magnetic resonance imaging (fMRI) to scan the brains of experienced and novice meditators as they practiced three different techniques. When the default network was active, regions associated with cognitive control and self-monitoring—which keep the brain on task and prevent the mind from wandering—were also active in experienced meditators but not in novices. This co-activation happened even when they weren’t meditating, suggesting that meditators may be constantly monitoring mind-wandering and “me”-centered thoughts. Brewer believes that over time, the meditators may have developed a new default mode in which there is more present-centered awareness and less self-centered thought.

Bob Agoglia, executive director of the Insight Meditation Society in Barre, Mass., who participated in the study and has been practicing meditation daily for over 30 years, isn’t surprised that meditation appears to be responsible for long-lasting changes in the brain. Two years ago he underwent major surgery. As he was waking from the anesthesia, he experienced intense pain quickly followed by fear. Suddenly, without any conscious intention on his part, the phrases he uses in his daily meditation began going through his mind and he relaxed immediately. “It was an unforgettable example, but on a daily basis it happens in much more subtle ways that are not quite as memorable,” he said.

Even those who had no experience with meditation before the study—novice participants received instruction just before undergoing the fMRI—were able to see its benefit. “It was almost like resetting my mental state,” said Kirk Snyder, 29, who felt a calm focus while meditating.

Despite the promise of meditation in the clinical setting,  Brewer’s colleagues were lukewarm when he first suggested studying it. “The old me would have thought it was too touchy-feely,” said David McCormick, Ph.D., Dorys McConnell Duberg Professor of Neurobiology. “But after having directly experienced meditation and how it can change your day-to-day perceptions, I’m much more interested in the neuroscience behind it.” McCormick began practicing meditation about three years ago because he was intrigued by the idea of having greater control over his mind and decreasing anxiety and stress.

Brewer hopes to translate the study’s findings into more clinically viable tools. He’s done a follow-up study in which experienced and novice meditators viewed real-time feedback of activity in their own posterior cingulate cortex. The subjects reported a strong correlation between mind-wandering and an increase in activity in this region, but a decrease in activity when they were meditating. Brewer believes that this type of neurofeedback may help patients learn how to meditate correctly, thereby increasing the therapeutic benefit of the practice.

Learning how to practice meditation rapidly is important because many people find it difficult to maintain. Brewer likens the process to traipsing through a river with mud on the bottom. At first the water is cloudy because the mud is stirred up, but eventually it washes downstream. “If you keep practicing you’ll keep that mud from depositing on the bottom in the future,” he said. “That analogy is what we have found clinically.”