Monday, April 19, 2010

Meditation, Cortical Thickness, and Pain Sensitivity

There’s a small but growing body of research literature showing that meditation practice is associated with greater cortical thickness in the brain (i.e., Grant et al., 2010; Lazar et al., 2005; Pagnoni & Cekic, 2007). All three studies used MRI scans to examine brain structures. In Lazar et al. (2005), a group of Insight meditation practitioners, regions of the brain associated with attention and sensory processing exhibited an increased thickness compared to a control group matched for gender, age, race, and years of education. Interestingly, the average thickness in the prefrontal cortex in 40-50 year-old meditators was similar to the average thickness of 20-30 year-old meditators and controls. This suggests that practice may slow age-related degeneration of brain tissue. Pagnoni & Cekic found a similar pattern in Zen practitioners.

More recently, Grant et al. (2010) examined the relationship between cortical structures and pain sensitivity in meditators. The researcher first compiled a list of 68 meditators willing to participate. In order to have a more homogenous sample, they chose Zen practitioners, who both made up the largest tradition in the list and reported more than 1,000 hours of meditation experience. Of the 19 Zen practitioners, 17 participated; these were matched against 17 non-meditators for age and gender.

A computer controlled increase in temperature, which was designed to create a moderate level of pain, was applied to the inner left calf of each participant. Cortical size was measured using MRI scans.

Zen practitioner exhibited lower pain sensitivity than controls. On average, Zen practitioners required an increase to 50°C in order to report a moderate level of pain; controls required an average of 48°C. Lower pain sensitivity was also related to greater cortical thickness, particularly in the dorsal anterior cingulated cortex, right anterior insula, and bilateral hippocampal formation. Greater thickness in these areas was related to greater meditation experience. Because this was a cross-sectional study and not a true experiment, we can’t be certain that there is a causal relationships between meditation experience, cortical thickness, and pain sensitivity. Taken together, the authors suggest that long-term meditation practice may lead to changes in the brain structures, which in turn may lower sensitivity to physical pain. The full article can be read in the most recent edition of the scientific journal Emotion. Interview excerpts with the first author about this study can be found at Science Daily.

A PDF of the Lazar et al. (2005) article can be found at the first author’s website.

The citations for the articles are:

Grant J.A., Courtemanche J., Duerden, E.G. Duncan G.H., & Rainville, P. (2010). Cortical thickness and pain sensitivity in zen meditators. Emotion, 10(1), 43-53.

Lazar, S. W., Kerr, C. E., Wasserman, R. H., Gray, J. R., Greve, D. N., Treadway, M. T., et al. (2005). Meditation experience is associated with increased cortical thickness. Neuroreport, 16(17), 1893-1997.

Pagnoni, G., & Cekic, M. (2007). Age effects on gray matter volume and attentional performance in Zen meditation. Neurobiology of Aging, 28(10), 1623-1627.

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