Monday, February 7, 2011

Mindfulness Practice Leads to Increases in Regional Brain Gray Density Matter

Last week, I posted a New York Times article about a study looking at brain changes following an 8-week mindfulness program. As promised, I've since read the study on which the article was based and am posting my own summary.

Lead by Dr. Britta Hölzel, a group of researchers, mainly located at Massachusetts General Hospital, examined changes in the brain following an 8-week Mindfulness-Based Stress Reduction (MBSR) program. As I've posted about before, previous research has indicated differences in cortical thickness in areas of the brains of experience meditators compared to age-matched control groups. The weakness of the previous studies is that it doesn't rule out that people with pre-existing differences in brain structure may be more likely to gravitate towards meditation.

In the current study, the researchers conducted MRI scans of 16 people 2 weeks before and 2 weeks after an 8-week MBSR course. This scans were compared against a control sample of 17 people on wait list for the course. Researchers scanned the wait list group twice about 2 months apart. In addition the scans, participants also completed the Five-Facet Mindfulness Questionnaire (FFMQ; Baer et al., 2006), a self-report measure of mindfulness.

As the researchers predicted, MBSR participants showed significant increases in gray matter density in the left hippocampus, an area of the brain associated with arousal, responsiveness, and emotion regulation, according to the researchers. They suggest these changes may reflect improvements in regulating emotional responding. These changes were unrelated to self-reported mindfulness scores on the FFMQ and to the amount of time people practiced mindfulness outside the course. Contrary to the researchers' predictions, there was no changes in the insula, a region of the brain associated with awareness.

I'll note here that the researchers predicted changes in the hippocampus and insula prior to conducting the study. After looking at these regions, they also conducted exploratory analyses to examine whether there were changes in other parts of the brain that they did not make specific hypotheses about. What this means is that the researchers had no prior expectations about whether these other areas would change. Since they had the data, they thought, "Hey, let's take a look!" There's nothing wrong with this, but it does mean these results should be interpreted more cautiously, since there were no prior reasons to believe they would change.

These exploratory analyses found increases in density in the posterior cingulate cortex (PCC), the left temporo-parietal junction (TPJ), and in two regions of the cerebellum. In addition, there were changes in density within the brain stem. In the interests of space, I'll give a more general summary of the functions associated with these regions. According to the researchers, these regions of the brain appear to be associated with consciousness of one's self (TPJ), assessment of the self-relevance of stimuli (PCC), regulation of emotion and cognition (cerebellum).

This is a general summary of what the study found. As I'm not an expert in neuroscience, any errors in what I reported are likely mine. I encourage anyone interested to consult the original study if you want more detail.

Although this study shows greater methodological rigor in controlling for other possible influences other than meditation, as the authors note, their methodology is not completely airtight. Perhaps the biggest weakness is comparing a wait list control group against an active treatment. It's perfectly reasonable comparison, but the downside is that it doesn't control for the possibility of non-specific factors other than meditation influencing outcome. Said less technically, simply being in a group for 8 week may have caused changes independent of the actual mindfulness practices. In addition, the sample size is pretty small--which is understandable as neuroimaging research is expensive!

These caveats aside, this is a really important study in gathering further evidence that people may show actual physical changes in relevant areas brain through mindfulness practice. That significant differences were shown with only 8 weeks of mindfulness practice is pretty remarkable.

To download the article, click on the citation below:

Hölzel, B.K., Carmody, J., Vangel, M., Congleton, C., Yerramsetti, S.M., et al. (2011). Mindfulness Practice Leads to Increases in Regional Brain Gray Density Matter. Psychiatry Research: Neuroimagining, 191, 36-43.

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