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Research shows how meditation affects the brain

By now, there’s enough research on meditation to show that it reliably has positive effects on well-being. But even though researchers know that meditation seems to make people feel better, they’ve argued about which mechanisms – and which parts of the brain – are involved. Investigators are now trying to solve this riddle by designing new and more rigorous experiments. Two recent articles by well-known meditation researchers demonstrate this trend, providing some intriguing insights into how meditation affects the physical brain.

The first study, published in the journal Brain Research Bulletin, focuses on localized brain wave modulation – specifically, how people can hone their attention by altering their brain wave patterns. Authored in part by Dr. Catherine Kerr, an expert in the placebo effect, alternative medicine, and meditation, the paper draws its inspiration from previous studies showing that alpha wave (seven-14 Herz) modulation helps people to pay attention to selective stimuli. In essence, increases in alpha waves in a given part of the brain prevent distracting information from passing through that part, while decreases in alpha waves enhance the ability of stimuli to be transmitted.

In practical terms, this means that alpha wave patterns can be used to determine how much information is presenting itself to specific parts of the brain that are correlated with different regions of the body. These areas are primarily found in the somatosensory cortex – a thin region of the brain that directs sensation and muscle action for the whole body. Each part of the body has a specific area in the somatosensory cortex that “lights up” when that part is touched or when the brain tells that part to move. When someone pays attention to one part of his or her body – the left index finger, for example – alpha waves in the parts of the brain surrounding the left index finger representation area increase, preventing distracting data from passing through and  interfering with signals coming in from the finger. Meanwhile, alpha waves in the left finger representation area will be decreased, allowing data from that part of the body to pass through intact.

Kerr and her colleagues studied a small group of meditators and non-meditators to see whether long-term meditation experience could help people more effectively modulate alpha rhythms – not just whole-brain alpha waves, but the specific, localized patterns that correlate with attention to a particular place on the body. The participants were divided into one control group and a meditation group that received Mindfulness-Based Stress Reduction (MBSR) training for eight weeks. The investigators used a magnetoencaphalograph (MEG) machine to record localized brain-wave patterns at the beginning of the study and once more at the end. While the recordings were being taken, the subjects were given light tactile stimuli to either their middle left finger or their big left toe.

As the investigators expected, over the course of the study there were big changes in the alpha wave patterns in the parts of the meditators’ brains that correlated to their respective fingers and toes. Specifically, subjects who had undergone meditation training showed a much greater difference between the alpha waves in the finger and toe representation areas and those in the surrounding parts of the somatosensory cortex than their non-meditating peers. The authors interpreted these results to mean that even a short course of meditation training helps people’s brains become better at using alpha-wave changes to selectively filter out unwanted or irrelevant data – making it easier to pay attention to the information that really matters.

Of course, it’s clear to everyone that meditation can help people focus better. But some studies suggest that meditation can also improve general mood and help people regulate their emotions. Researchers from Toho University in Japan recently published a paper in the International Journal of Psychophysiology showing that these effects could, in part, be due to increased serotonin levels in the blood. They were inspiredby pevious studies that had suggested that serotonin production could be stimulated by voluntary repetitive action – such as ritual bowing or singing or, in the case of meditation, regular, intentional breathing.

The researchers gave Zen meditation training to a small group of volunteers, teaching them to focus particular attention on the lower part of their abdomen during breathing. Using a special technique known as near-infrared spectroscopy (NIRS), the investigators were able to record changes in the blood-oxygen levels of the subjects’ brains as they meditated. What they found aligned with their expectations: Zen meditation appeared to increase blood-oxygen levels in the very front parts of subjects’ brains, in the area known as the anterior prefrontal cortex. This region is highly involved in paying attention – especially to emotionally engaging stimuli – and sifting out extraneous data.

Unsurprisingly, this increase in focus and attention was accompanied by enhanced alpha wave activity. Using prior research that linked serotonin levels with increased alpha activity in animals, the researchers suggested that the regular, intentional breathing characteristic of Zen meditation actually increased serotonin production in the brain, which in turn prompted the brain to increase alpha wave activity. These boosted alpha levels essentially calmed many parts of the brain down, helping the subjects to focus and remain clear-headed. The investigators’ hypothesis was backed up when they found increased levels of serotonin in the subjects’ blood after meditation.

Both these studies seem to point to alpha waves as one mechanism that meditation engages in order to have positive effects on people’s brains. (But see here for an article on gamma waves and meditation.) And the Japanese study also links meditation to enhanced serotonin levels – perhaps an unsurprising result for anyone who’s meditated or prayed and felt better afterwards. But, while these and similar studies certainly help advance our understanding of meditation and other spiritual practices, they raise as many questions as they answer. For example, do the localized alpha wave changes seen in Kerr et al.’s study also stem from increased serotonin production? What other neurotransmitters can meditation have an effect on? And do different styles of meditation have different effects on brain wave activity and serotonin levels?

Given that meditation shares many characteristics with other religious practices – such as its often repetitive, intentional nature, as in focused breathing – it’s hard not to wonder whether these findings and the questions they raise also apply to phenomena such as shamanic trances, ritual prayer, and other religious experiences. As long as researchers keep training their lenses on meditation and its effects on the human body, we’ll come closer every day to finding out.