Effect on brain structure (review & meta-analysis)

Fox, K. C., et al. (2014). Is meditation associated with altered brain structure? A systematic review and meta-analysis of morphometric neuroimaging in meditation practitioners. Neuroscience & Biobehavioral Reviews, 43, 48-73. Full text.

From the Abstract: Numerous studies have begun to address how the brain’s gray and white matter may be shaped by meditation. This research is yet to be integrated, however, and two fundamental questions remain: Is meditation associated with altered brain structure? If so, what is the magnitude of these differences? To address these questions, we reviewed and meta-analyzed 123 brain morphology differences from 21 neuroimaging studies examining ∼300 meditation practitioners.

Anatomical likelihood estimation meta-analysis found eight brain regions consistently altered in meditators, including areas key to meta-awareness, exteroceptive and interoceptive body awareness (sensory cortices and insula), memory consolidation and reconsolidation (hippocampus), self and emotion regulation (anterior and mid cingulate; orbitofrontal cortex), and intra- and interhemispheric communication (superior longitudinal fasciculus; corpus callosum).

Increases gray matter concentration

Hölzel, B.K., et al. (2011). Mindfulness practice leads to increases in regional brain gray matter density. Psychiatry Research, 191 (1), 36-43. Full text (unedited manuscript).

From the Abstract: Therapeutic interventions that incorporate training in mindfulness meditation have become increasingly popular, but to date little is known about neural mechanisms associated with these interventions. Mindfulness-Based Stress Reduction (MBSR), one of the most widely used mindfulness training programs, has been reported to produce positive effects on psychological well-being and to ameliorate symptoms of a number of disorders.

Here, we report a controlled longitudinal study to investigate pre-post changes in brain gray matter concentration attributable to participation in an MBSR program. Anatomical magnetic resonance (MR) images from 16 healthy, meditation-naïve participants were obtained before and after they underwent the 8-week program.

Changes in gray matter concentration were investigated using voxel-based morphometry, and compared with a waiting list control group of 17 individuals. Analyses in a priori regions of interest confirmed increases in gray matter concentration within the left hippocampus. Whole brain analyses identified increases in the posterior cingulate cortex, the temporo-parietal junction, and the cerebellum in the MBSR group compared with the controls.

The results suggest that participation in MBSR is associated with changes in gray matter concentration in brain regions involved in learning and memory processes, emotion regulation, self-referential processing, and perspective taking.

Brain changes in ‘loving kindness’ meditators

Leung, M.K., et al. (2012). Increased gray-matter volume in the right angular and posterior parahippocampal gyri in loving-kindness meditators. [Abstract]. Soc Cogn Affect Neurosci. Published online. Full text.

Previous voxel-based morphometry (VBM) studies have revealed that meditation is associated with structural brain changes in regions underlying cognitive processes that are required for attention or mindfulness during meditation. This VBM study examined brain changes related to the practice of an emotion-oriented meditation, namely, loving-kindness meditation (LKM). A 3T MRI scanner captured images of the brain structures of 25 men, 10 of whom had practiced LKM in the Theravada tradition for at least 5 years.

Compared with novices, more gray-matter volume was detected in the right angular and posterior parahippocampal gyri in LKM experts. The right angular gyrus has not been previously reported to have structural difference associated with meditation and its specific role in theory of mind and cognitive empathy suggest the uniqueness of this finding to LKM practice. These regions are important for affective regulation associated with empathic response, anxiety, and mood. At the same time, gray matter volume in the left temporal lobe in the LKM experts appeared greater, an observation that has also been reported in previous MRI meditation studies on meditation styles other than LKM.

Overall, the findings of our study suggest that the experience with LKM may influence brain structures associated with affective regulation.