Abby Tabor
A new study has found that the brains of people who meditate show greater folding, with more peaks and valleys, than those of people who don’t. The region most significantly implicated plays a role that may, indeed, be involved in meditation. If this practice can be shown to cause the neural differences observed, meditation may provide a method to protect the brain from some aspects of aging, in addition to the benefits it is already known to have.
On Monday, March 26, 2012, the Institut de France, in Paris, will host the first in a series of seminars on the subject of modified states of consciousness – such as those seen under hypnosis, during hallucinations, or in meditation – viewed from scientific, legal and philosophical standpoints. For more information and a schedule of the day’s events: Les états modifiés de conscience sous le regard des scientifiques, juristes et philosophes
Meditation is known for its positive effects on stress levels, mental health and self-control. The way this corresponds to specific characteristics of the brain has also been studied, although cause and effect remains a gray area. A 2009 study, for instance, showed that the brain of a person who meditates tends to have larger volume in certain regions known for regulating emotions. A March 2012 study at the UCLA School of Medicine (Los Angeles) has shown for the first time that meditation may also be connected to greater folding of the surface of the brain, which may encourage more connections and faster neural processing. It is too soon to draw any firm conclusions about cause, but the correlation suggests some intriguing possibilities.
The cerebral cortex is the outermost layer of the brain and is involved in higher-level processing, like thought, memory and attention. Gyrification, or the folding of the cortex, creates small furrows and ridges all over the surface. Called sulci and gyri, these folds are believed to increase the surface area of the brain, maximizing the possibility for connections among neurons.
Eileen Luders, an assistant professor at UCLA’s Laboratory of Neuro Imaging, and her team wanted to know if there is a connection between meditation and the amount of gyrification. Their findings show not only that meditators have more cortical folding in certain regions than non-meditators, but that the number of years of practice is directly correlated to the degree of gyrification.
The researchers compared MRI scans of the brains of 50 meditators and 50 non-meditating control subjects, matched in pairs by age and sex. The experimental subjects had been meditating for an average of 20 years, their experience ranging between four and 46 years. The team measured gyrification of the cortex by comparing thousands of points across the surface of the brain and calculating the mean curvature of the sulci and gyri.
Their results showed that meditators had significantly more folding in a number of regions of the brain. Interestingly, some of these regions had already been shown in other studies to be related to meditation: practitioners’ brains were found to be thicker here, consisting of more gray matter, than non-meditators.
Comparison within the group of meditators also revealed significant differences, with long-term practitioners showing more gyrification than beginners in several brain regions. In both comparisons – between meditators and control subjects, long-term practitioners and newer converts – one area stood out as the most significantly different between groups. Researchers had already characterized a role for this region, the right anterior dorsal insula, that may be involved in meditation: it controls the switching on and off of a neural system known as the default-mode network (DMN). The DMN is most active when we are daydreaming, letting our mind wander, or imagining ourselves in the past or the future. These are all mental activities that risk distracting someone in meditation. The authors suggest that being able to meditate successfully might involve a better ability to control the DMN, and that the more complex gyrification of the right insula might be an anatomical basis for this skill.
Another role described for the insula involves awareness of one’s own physiological state, as well as sensitivity to an array of stimuli, be it thoughts, feelings, smells, tastes... It seems that the insula serves as a center for integrating all this diverse input, which would be in line with meditation’s focus on introspection and emotional control.
Luders et al. address the question of nature versus nurture regarding the brain differences seen between those who meditate and those who do not, acknowledging that it is likely an interaction between the two. About 30% of differences in brain folding can be attributed to genetics. The particular pattern of gyrification is especially dependant on one’s genes. But the degree of gyrification has been shown to change through adolescence, suggesting that this aspect is susceptible to environmental factors. If, indeed, the amount of folding of the cortex can continue to be modeled throughout life, the authors suggest that meditation, particularly when practiced over a long period, may create changes in the brain. They think this plasticity could occur, for example, on the level of synapses that are pruned or dendrites that create new connections.
The UCLA team acknowledges that, at this point, conclusions drawn from their findings can only be speculative. However, the future studies that they suggest open doors to tantalizing new questions. Further investigation could help to identify any difference between effects produced by sulci versus gyri. This, in turn, may shed light on a possible effect of meditation, already observed, in preserving the brain from certain effects of aging. The shape of the ridges and valleys of the cortex are known to change with age. If meditation really is able to provide some protection against these alterations, the consequences should be visible in their brains.
Meditation may be a practice as old as our oldest religions, but its secrets remain largely hidden from us. In recent years, there has been growing evidence that this practice is not just a cultural artifact but a real human skill able to modify the brain at multiple levels. The discovery of increased gyrification linked to meditation provides more evidence of a possible effect on brain anatomy. This will encourage future investigation towards a better understanding of meditation and its potential application to neurodegenerative disease and brain aging.
To find out more: National Center for Complementary and Alternative Medicine, National Institutes of Health, « Meditation » https://www.nccih.nih.gov/health/meditation-in-depth Transdisciplinary Research on Hallucinations and Other States of Modified Consciousness: Report #26 from PIRSTEC, of the French National Center for Scientific Research (CNRS). Download report (in French) here. Structural Brain Mapping Group at the University of Jena http://dbm.neuro.uni-jena.de/research/gyrification-and-cortical-measures/ Brainmapping.org: Dedicated to the communication of news, science, and information of interest to the brain mapping community, and to sharing and promoting the science of brain mapping. http://brainmapping.org/
