IN FOCUS: Meditation research
- Published on 27 February 2011
- Written by Connor Wood
- Hits: 4314
There’s no such thing as generic “meditation,” of course – every time someone sits down on a cushion or begins chanting a mantra, that person is taking part in a specific tradition with its own rules and practices. Some meditation styles use repetitive chanting, for example, while others instruct practitioners to focus on the breath. The articles presented here range across different styles and traditions of meditative practice, from a Korean rhythmic movement meditation to American-developed Mindfulness-Based Stress Reduction (MBSR). As you might expect, these very different styles of meditation gave rise to some different, and even sometimes contradictory, results.
For example, in an article in the Journal of Alternative and Complementary Medicine, Maria Engström and colleagues (Linköping University, Sweden) found that moderately experienced mantra meditators showed greater activation in the prefrontal cortex, as well as the hippocampus and the parahippocampal area, when they were meditating than when they were simply repeating a neutral phrase. This latter finding was considered unsurprising, since many previous studies on meditation had found that the hippocampus, an area of the brain related to memory, learning, and emotional interpretation and regulation, was apparently activated by mediative practice.
But in a study conducted by Joshua A. Grant and his colleagues at the University of Montréal and published in the journal Pain, highly experienced Zen practitioners who were subjected to painful experiences showed less, not more, activation in their hippocampi (like many midbrain structures, the hippocampus is actually comprised of two halves, one in each hemisphere). The authors weren’t surprised, though: they hypothesized that the reduced activation in the hippocampus was because Zen Buddhism trains its practitioners not to judge their experiences, but simply to acknowledge and observe them – and the hippocampus, along with the amygdala and prefrontal cortex, is an area associated with evaluating and judging experiences.
Instead, the Zen practitioners showed increased functioning in the thalamus, insula, and anterior cingulate cortex during painful stimulus. Interestingly, these areas are known as centers for processing and relaying pain signals. So, while Zen experts appeared not to be emotionally entangled with their painful experiences (pain was inflicted using a carefully heated – but not dangerous – metal instrument), they did seem to be somehow experiencing the pain more directly.
An important feature of Grant’s Zen study was that the experimental group was specifically instructed not to meditate during the procedure. Grant and his colleagues hoped to learn about to Zen practitioners’ everyday default state, hypothesizing that years of Zen practice affects people’s perception of pain even when they’re not sitting on the cushion. And, indeed, the Zen practitioners needed significantly higher temperatures to experience the same level of subjective pain as the control group, and showed different patterns of brain activation.
Returning to the hippocampus, while experience with Zen apparently reduces hippocampal activity during the experience of pain, research published by Danny Wang (UCLA) and colleagues in Psychiatry Research: Neuroimaging suggests that breath-based meditation strongly increases cerebral blood flow in the hippocampus and parahippocampus. (Cerebral blood flow is directly correlated to levels of activity in a given structure.) These findings are more typical of the plurality of meditation imaging studies: other areas activated by breath-based meditation in this experiment were the insula (another area often found to be affected by meditation), the amygdala, and the left superior temporal lobe. The hippocampus and amygdala together are both parts of what is commonly known as the “limbic system,” which is intimately related to, and a major driver of, our experience of emotion. It’s not surprising, then, that participants in this study rated the breath-based meditation as more subjectively intense than an alternative, focus-based meditation, which activated the medial prefrontal cortex – an area implicated in focus and directed attention.
Okay, so breath-based meditation helps people deal with emotions, and focus-based meditation helps build their attention skills. Clear enough. But wait – not so fast. Focused attention – a mental ability that many meditation styles work to develop – comes in different forms depending on what we’re paying attention to. In an article in Neuroscience Letters, Joon Hwan Jang and colleagues at Seoul National University and Seoul’s National Medical Center showed that regular brain-wave vibration meditation practitioners had better connections between the medial prefrontal, anterior cingulate, inferior parietal, and lateral temporal cortices, connections that were found even when subjects weren’t actively meditating. These areas, together known as the default mode network, are associated with introspective attention – that is, cognition that isn’t associated with any particular outside stimulus. The authors interpreted their findings to imply that experienced meditators may be better-equipped to maintain internally oriented attention. However, because their sample comprised practitioners of a unique Korean meditative style, they cautioned that their findings might not be easily generalized to other types of meditation. Other meditative styles that train people to, say, focus on external stimuli, or chant mantras, might develop parts of the brain associated with those types of attention.
Still, the theme of these and many other research studies appears clear: meditators seem to have different brains than non-meditators, even when they’re not meditating right at the moment. In other words, the normal, everyday resting state of a long-term meditator’s brain looks like it might be very different from the resting state of a non-meditator’s brain.
Superstar neuroscientist Andrew Newberg of the University Pennsylvania has long been a proponent of this view, and in a recent publication in Consciousness and Cognition he and a group of colleagues added yet more evidence to the pile. They studied a small group of experienced focus meditators using SPECT (single-photon emission computed tomography) scans, and found that the meditators’ baseline cerebral blood flow was significantly, and predictably, different than the baseline blood flow in a control group. Specifically, experienced meditators showed more baseline activity in the frontal cortex, thalamus, limbic system (although, perhaps unexpectedly, not the hippocampus), and the parietal cortex.
The elevated blood flow levels in this final structure came as a surprise to Newberg and his team. Activity in the parietal lobe is often reduced during different forms of meditative practice. The parietal lobe helps orient the body in space and maintain a sense of the body’s integrity and independence from other objects, and many researchers have suggested that reduced electrical activity in the parietal region is the reason meditators experience feelings of oneness, lack of individual boundaries, and connectedness during deep meditation.
However, the subjects in Newberg’s study weren’t meditating during the actual imaging. In fact, they’d been instructed not to meditate at all the day of the scan, so their cerebral blood flow readings truly showed their baseline status. But this might be a clue as to why experienced meditators often encounter such profound experiences of oneness: the researchers proposed that the elevated blood flow levels in the meditators’ parietal lobes during the resting state implied a greater drop in activity during meditation – leading to a correspondingly greater subjective sense of oneness and connection.
This is Part One of a two-part article. Check back soon – Part Two will be posted shortly!