Meditação... contemplação... apreciação... A atenção flexível... "Your Brain on Meditation AUGUST 20, 2013 BY JUDSON BREWER A new technology allows researchers to see the contemplative brain in real time—and uncover game-changing insights on everything from contentment to effort to distraction. We’ve all read or heard about scientific studies linking meditation to brain activity. These can be helpful in many ways. Maybe they help give us a little boost of motivation when we are deciding between hitting the snooze button or getting up to meditate early in the morning—“yes, this does change my brain!” Or perhaps these studies teach us something about how such rewiring affects the brain on a mechanistic level so scientists can learn a bit more about how the brain works. But what do we really know about meditation and the brain? There have been a number of studies that have shown that meditation lights up certain brain regions, that it’s associated with changes in brain thickness, and that it alters the way our brains respond to stressful stimuli. But meditation is complex, and it involves processes like attention, working memory, and self-monitoring. So, which components of meditation actually line up with specific brain regions? To dive into this question a bit more, we focused on a particular brain region called the posterior cingulate cortex. This part of the brain gets activated when folks are thinking about themselves, daydreaming, and/or craving certain substances—and importantly, gets deactivated during a number of different types of meditation (Brewer et al., 2011). In the past, traditional fMRI studies tended to average brain activity over a block of time (usually several minutes), average it again over several blocks within an individual, and then average it yet again over a number of subjects within a group (e.g. expert meditators vs. novices). These studies tell us on average what happens in the brain during meditation when studying X. But that is a lot of averaging. And anyone who has meditated for more that 15 seconds knows that the experience during a block of meditation can fluctuate tremendously. When we sit down to meditate, we drop in but then get distracted; we may bring our attention back to the object, then realize that we are tense or forcing the experience so we relax a little; and so on. Taking all this into account, we used a relatively new technology called real-time fMRI neurofeedback to ask a simple question: “How does the subjective experience of meditation line up with activity in the posterior cingulate cortex on a moment-to-moment basis?” With this technology, we can look at brain activity virtually in real time with the possibility of tracking all of those fluctuations that happen during meditation. Here, instead of averaging across a bunch of individuals, we can look at the individual variability within single runs within single subjects such that we can link subjective experience more precisely with brain activity. Our experiment went as follows: We put experienced meditators from several different traditions (Christian, Zen, Tibetan, Theravada) into our fMRI scanner and asked them to meditate with their eyes open for one-minute blocks of time. Immediately afterward, we asked them to describe their experience and how it may have changed from beginning to end. (We tried longer blocks of meditation, but meditators were finding it difficult to recall even two-minute blocks—lots can happen in two minutes!). The kicker was that while they were meditating they were also passively viewing a graph that was slowly filling in over time (a new bar every two seconds); that graph was showing them whether activity in their posterior cingulate cortex was increasing or decreasing. Their job was to check in with the graph from time to time to see how it was lining up with their meditative experience. For example, if they were deep in meditation for a period of time, immediately after they could check with the graph to see if it corresponded with increased or decreased activity of this brain region. To make sure they weren’t fooling themselves—or telling us what they thought we would want to hear—we did not tell them anything about what brain region we were looking at, or which direction the graph “should” go during periods of meditation. They had to discover this for themselves. And after a few runs where they meditated while passively viewing the graph—and then described how it lined up with their experience as a validation step—we then instructed them to make the graph go in the direction they had described as “meditation.” If their descriptions were accurate, they should be able to manipulate this brain region “on demand.” What did we find? First, confirming our and other studies of average activation of the posterior cingulate during meditation (Brefcynski-Lewis et al., 2007; Brewer et al., 2011; Pagnoni, 2012), meditators reported that decreased activity in this brain region correlated very well with meditation (Garrison et al., 2013b). Second, meditators could significantly decrease posterior cingulate activity on demand whereas novice meditators could not. And third, there was more to meditation and the posterior cingulate than met the eye. For example, when we asked folks to describe their experience after each block of meditation, we got a lot of descriptions like: “I was concentrating at the beginning, and it lined up with the graph going down” and “I got distracted and the graph went up.” (Garrison et al., 2013a) This was good and expected and fit nicely with the literature. But perhaps not surprisingly, we also got a lot of different descriptions of people’s experiences, likely because people have a lot of different experiences during meditation. Folks described times when they just relaxed and watched thoughts arise, moments when they became anxious, even moments when they tried to concentrate more. This produced a trove of rich subjective experience that we could directly tie to brain activity! We took all of these subjective descriptions and put them into general categories such as “concentration” and “distraction.” Because of all of the other descriptions, we had to come up with new categories such as “efforting” for when folks described trying to do something (it turned out that the trying was more important than the thing they were trying to do), and “not efforting” when people were just effortlessly aware of their breath or their experience or even the graph. We then looked at all these categories to see how they lined up with posterior cingulate activity. For example, there were 99 instances in which individuals reported being “concentrated” and that lined up with the graph decreasing; there were 64 instances when people reported being distracted and that lined up with increases in the graph. These data were great—for the first time, we had a much more nuanced picture of how the posterior cingulate links to the subjective experience of meditation on a moment-to-moment basis. Besides just showing that this brain activity goes down during meditation and up during distraction, the experiment also revealed a number of other subjective experiences that are part of meditation that also corresponded with posterior cingulate cortex activity, such as contentment (decreased activity), “not efforting” (decreased activity), discontentment (increased activity), and “efforting” (increased activity). Obviously, this is just a first step in learning how to use these tools effectively to study how the subjective experience of meditation lines up with brain activity, and there is a lot more to be explored. After all, the posterior cingulate cortex is one very small part of the brain. But these data also showed that we can start to use techniques such as real time neurofeedback to more precisely link brain activity with subjective experience across a number of realms of cognitive neuroscience (meditation just being one of them). And in the future, we may even be able to bring these neuroscience tools together to help provide feedback while individuals are learning to meditate. To see this and other related papers on neurophenomenology, check out this special issue of Frontiers in Human Neuroscience, edited by Mind and Life’s Senior Scientific Officer, Wendy Hasenkamp, and Mind and Life Fellow Evan Thompson. Click on the “Articles” tab to see the entire collection. More papers will be added in the coming months! Judson BrewerJudson Brewer, MD, PhD, is the medical director of the Yale Therapeutic Neuroscience Clinic and an assistant professor at the Yale University School of Medicine. A psychiatrist and internationally known expert in mindfulness training for addictions, Brewer has developed and tested novel mindfulness programs for addictions, including both in-person and app-based treatments. He has also studied the underlying neural mechanisms of mindfulness using standard and real-time fMRI, and is currently translating these findings into clinical use. He has published numerous peer-reviewed articles and book chapters, spoken at international conferences, given a TEDx talk, and been interviewed by media avenues such as Forbes, NPR and the BBC. He writes an addiction blog for The Huffington Post. Texto em: mindandlife.org/your-brain-on-meditation/
Posted on: Sat, 24 Aug 2013 20:22:39 +0000
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