As the spiritual leader of Tibetan Buddhism, the Dalai Lama was intrigued that scientists had found evidence that some parts of the brain might renew themselves throughout life. The discovery seemed to fit well with the Buddhist view that meditation can reshape and expand the mind to foster happiness and cultivate compassion.
In a November speech, the Dalai Lama made the connection between neuroscientists' research into brain mechanisms associated with attention and emotion and Buddhist meditation that is performed to heighten powers of attention and regulate emotion.
"I feel there might be great potential for collaborative research between the Buddhist contemplative tradition and neuroscience," he said at the Society for Neuroscience annual meeting.
People have studied the connections between meditation and brain physiology for years.
Can science identify a physical signature of that effort somewhere in the vast landscape of the brain?
Only recently has research been rigorously performed, fuelled by two developments. One is neuroscientist Fred Gage's 1998 discovery, subsequently confirmed and extended, that new cells can, in fact, grow in the adult hippocampus, an area of the brain associated with learning, memory and emotion. It had long been thought that cell growth stopped in the adult brain. The other is the continual refinement of technology used to image and measure changes in the brain.
In the early 1990s, American scientist Richard Davidson travelled to India at the request of the Dalai Lama to meet with Buddhist monks who devote their lives to meditation. A Harvard-educated researcher at the University of Wisconsin, Davidson has since brought Buddhist monks to his lab. There he has hooked them up to an electroencephalograph, or EEG, that measures changes in the electrical activity of the brain.
Brain cells communicate by producing tiny electrical impulses. During EEG studies, researchers place several electrodes on a subject's scalp to detect and record patterns of electrical activity in the brain.
In his studies on monks, Davidson found that electrical activity was heightened during meditation in an area of the brain called the left prefrontal cortex, just behind the forehead. Scientists have associated activity in this region with positive emotions, as opposed to the right prefrontal cortex, where increases are associated with negative feelings.
More recently, Davidson has found that longtime Buddhist practitioners of meditation can induce a heightened pattern of electrical signals called gamma-band oscillations, associated with concentration and emotional control, that are not seen in control groups. These changes are sustained even after meditating.
Thickening the Brain
Sara W. Lazar is a neuroscientist and practises meditation. You don't often hear those in the same sentence. But the life of this one-time Ph.D. student in molecular biology changed course when she discovered yoga and meditation while recovering from a running injury. That was 12 years ago and now she is a cutting edge researcher in the field of neuroscience. She's focusing on the effects of meditation on the brain. "While in grad school I started practising yoga and meditation, and found it to be incredibly helpful. I was less stressed, more focused and it really changed my perspective on a lot of things. I decided I would rather do research on meditation than on bacteria so, after I got my Ph.D., I found a lab that was willing to train me in neuroscience and let me do a small meditation study."
That lab happened to be in the Psychiatry Department at Massachusetts General Hospital. The focus of her research is the neurobiology of meditation. She uses functional magnetic resonance imaging (fMRI) to investigate the neural correlates of changes in autonomic function during the practise of meditation. Dr. Lazar goes on to explain, "fMRI is a special way of using a MRI scanner to look at how the brain works. Normal MRI takes one really nice picture of your brain, with lots of details that are easy to see. fMRI is sort of like a movie - it takes special pictures of blood flow in the brain. The parts of the brain that are most active at any point will have the most blood flow, so we take pictures of the person meditating and resting, and then use a computer to determine where in the brain there is the most blood flow during meditation compared to rest." Dr. Lazar explains that an MRI scanner is sort of like an X-ray, but it allows us to take pictures of the brain.
Unlike Tibetan Buddhist monks, who have devoted their lives to the practise of meditation and their religion, meditation practitioners in the U.S. usually meditate just 20 to 60 minutes per day and incorporate their practise into a daily routine involving career, family, friends, and other outside interests, according to Lazar. Additionally, many American meditation students view meditation as a source of stress-reduction, mental exercise or personal growth, and do not necessarily incorporate traditional eastern religious elements into their practise.
Lazar and her colleagues compared the brains of 20 western-style meditators with 15 people who had no meditation or yoga experience. The meditators were students of Buddhist "Insight" meditation, which focuses on the cultivation of a trait called mindfulness, a specific, non-judgmental awareness of present-moment sensory stimuli. All study participants laid quietly in the MRI scanner while detailed images were taken of the structure of their brains.
"We found that brain regions associated with attention and sensory processing were thicker in meditators than in the non-meditators," says Lazar. "Also, in one of the regions, the differences in thickness were most pronounced in older subjects, suggesting that regular practise of meditation might reduce normal age-related thinning of the brain." This region is an area of the brain's outer layer or cortex, which is thought to be involved in integrating emotional and cognitive processes.
"Although numerous studies examining cortical thickness have pointed to ageing and pathology as sources of cortical thinning, there has been limited work indicating mechanisms promoting cortical thickening," says Lazar. "Our findings suggest that meditation practise can promote cortical changes in adults in areas important for cognitive and emotional processing and well-being."
It is possible that people who naturally have a thicker cortex in areas associated with awareness and sensory processing are more likely to practise meditation. However, the pattern of cortical thickening corresponds well to the specific activities that practitioners of Insight meditation repeatedly engage in over time: paying attention to breathing sensation and sensory stimuli, according to Lazar. Additionally, the observed increases in cortical thickness were proportional to the amount of time the participant had spent meditating over their lifetime.
"While additional research needs to be done, our results do suggest that the observed differences are acquired through extensive practise of meditation and are not simply due to incidental between-group differences," says Lazar. "We also believe that other forms of yoga and meditation would have a similar impact on brain structure."
It shouldn't be surprising that meditation alters part of the brain physiologically, scientists say. Musicians, linguists and athletes have thicker brain tissue in areas associated with their strengths and talents. "It makes sense that if you're using part of your brain a lot, it's going to get worked out and there's going to be more stuff in that area to support increased usage," Lazar said. "In a sense, that's all we're seeing."
In follow-up studies, she plans to study whether the increased thickness is correlated with increased attention and memory.
For the Sleepy
Other researchers from the University of Kentucky examined whether meditation might involve brain functions similar to sleep. Although meditation is a form of wakefulness, meditation, like sleep, is also reported to be relaxing and restorative.
Bruce O'Hara, from the University of Kentucky, has been interested in whether meditation can reduce the need for sleep. Might meditation be of value to people with sleep disorders or those whose jobs leave them sleep-deprived? O'Hara first put subjects to a psychomotor vigilance test (PVT), which is a simple measure of reaction time. During the test, subjects press a button as soon as they see an LED clock display begin to tick. Most alert people push the button after about 200 milliseconds. The test randomly repeats over 10 minutes, and a subject's results are closely correlated with how sleepy they are, going into the test.
Each subject, none of whom was an experienced meditator, took the test after spending 40 minutes in casual conversation, reading, sleeping or meditating. Only when the subjects meditated prior to the test did their scores improve.
"It was amazing how consistent it was," O'Hara said. "Twelve out of 12 of our first subjects all improved (on the test) following meditation."
O'Hara also tested subjects who deprived themselves of sleep the night before. Those who meditated right before the test performed better than those who did not. O'Hara next examined sleep-deprived subjects who took a nap right before the test. They actually did worse because it takes time to fully recover alertness after a nap.
During sleep, neurons fire with more synchrony than during wakefulness. In the deepest stage of non-REM sleep, the dominant brain wave is called a delta wave. During meditation, brain cells fire with a different synchrony that produces alpha waves. The question is: Can alpha waves be as restorative and therapeutic as delta waves?
In future studies, O'Hara plans to use EEG tests to examine whether a boost in alpha waves during meditation correlates with a commensurate drop in delta waves during sleep after meditating. Such a measurement might provide evidence that meditation does restore the brain in a way that requires less sleep, he said.
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