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  • Addiction, Drugs
  • Information from Lay-Language Summaries is Embargoed Until the Conclusion of the Scientific Presentation

    185—Individual Differences: Personality, Emotion, and Disorders

    Sunday, November 10, 2013, 8:00 am - 12:00 noon

    185.25: Increased weekly yoga practice leads to more brain gray matter

    Location: Halls B-H

    *C. VILLEMURE1,2, M. CEKO1,2, V. A. COTTON2, M. C. BUSHNELL1,2;
    1NIH, NCCAM, Bethesda, MD; 2Alan Edwards Ctr. for Res. on Pain, McGill Univ., Montreal, QC, Canada

    Abstract Body: We recently showed that experienced yoga practitioners have more gray matter than matched controls in multiple brain areas. These differences could be related to yoga practice itself or to other characteristics of yoga practitioners. Here we investigate whether gray matter increases in yoga practitioners are influenced by the amount of time devoted to yoga practice.
    We tested 14 North American individuals from various yoga schools who practiced postures, breath awareness and control, concentration, meditation and chanting Sanskrit mantras an average of 8.6 hours/week (SD: 4.1) with an emphasis on postures (66% of the total practice ± 21). Each subject had one anatomical MRI scan. We performed a whole-brain voxel-based morphometry regression analysis (cluster-corrected at p<0.05 using random field theory) with the number of hours/week devoted to yoga practice as the predictor and age as a covariate of no interest.
    We found that a higher frequency of yoga practice was associated with more gray matter in the right primary somatosensory cortex/superior parietal lobule (S1/SPL), right visual cortex, left hippocampus, and mid precuneus/posterior cingulate (PCC). Yoga involves interoceptive awareness. Hence, during the practice of yoga postures attention is devoted to the breath and to body alignment and position. This might be related to the increases in S1/SPL and precuneus/PCC volumes found with increasing practice frequency. SPL is involved in the voluntary orienting of attention and S1 contains a representational map of the entire body. The precuneus and PCC belong to a network of midline structures thought to be crucial for self-relevant processing. Increasing gray matter volume in all these areas could reflect an enhanced experience of one’s own body and breath related to an increasing amount of yoga practice. Increased gray matter volume in the visual cortex might be related to yoga practices involving visualisation such as yoga nidra. Previous studies found that the hippocampus is activated during yoga-related meditation and that larger hippocampi are found in meditators than in controls. The hippocampus is involved in the regulation of stress hormones through its projection to the paraventricular nucleus of the hypothalamus. Importantly, a relationship between hippocampal volume and the cortisol response has been reported in humans, with larger hippocampi associated with lower cortisol secretion in response to stressors. Our results suggest a link between increasing amount of regular yoga practice and brain volume increases in areas involved in somatosensation, attention, self-relevant processing, visualisation and stress regulation.

    Lay Language Summary: Our research suggests that the structure of our brain can be changed by regular yoga practice. Some of these anatomical changes are related to how much yoga a person does each week.
    This is interesting and important because it suggests that yoga practice itself shapes the brain as opposed to people practicing yoga having different brains from the start. Previous studies have shown that meditation practice is associated with brain structural changes. However, this is the first study relating yoga practice and changes in brain anatomy.
    However, not all areas of the brain were modified by the amount of time spent doing yoga. We found five brain areas that contained more gray matter with increasing number of hours of yoga practice: one is involved in touch and contains a map representing the entire body; the second area is involved in attention; the third is implicated in self-relevant processing like thoughts about ourselves; the fourth is engaged in visual processing; and the fifth is known to be involved in stress regulation.
    What it means to have more gray matter in certain brain areas is not completely understood. The most likely explanation is that the nerve cells in the areas involved make more connections with each other as these areas are particularly recruited during yoga practice. During the practice of yoga postures, attention is directed to the breath and body alignment and position, so it would not be surprising to see that more frequent practice may increase gray matter volume in brain areas involved in attention, self-relevant processes, and the area of the brain that contains a representation map of our body. Increased gray matter in the visual cortex may be related to certain visualization practices done in yoga. Yoga is also known to reduce stress so it is interesting that increasing amount of weekly yoga practice would impact on the size of a brain area known to be involved in the regulation of stress hormones. However, we cannot rule out that other factors are implicated, for example, an increase in the number of cells that are not necessarily involved in information transmission.
    In this study we tested 14 individuals who regularly practiced yoga but otherwise lead a typical life. The average age of the participants was 37 years old (minimum 30, maximum 50). On average they had practiced yoga for almost 10 years at the time of testing (minimum 6, maximum 16) and spent 9 hours/week practicing (minimum 4, maximum 18). They were from various yoga schools, but their practice involved mainly yoga postures (on average 66% of their practice), and to a lesser degree, breath awareness and control (on average 11% of their practice) and concentration and meditation practices including chanting Sanskrit mantras (on average 23% of their practice). Each participant had one anatomical scan that was analyzed taking into account the number of hours of yoga practiced each week.
    Because the yogis we tested were all experienced practitioners with more than 6 years of practice, we don’t know how long it takes for these brain changes to occur. Although our findings suggest that it is indeed the practice of yoga that increased gray matter in these brain regions, it would be useful to perform another study where people who never practiced yoga would enroll in regular yoga classes. This would verify whether yoga would modify their brain anatomy and determine how much yoga practice is necessary to get an effect.