By John M. de Castro, Ph.D.
“The practice appears to have an amazing variety of neurological benefits – from changes in grey matter volume to reduced activity in the “me” centers of the brain to enhanced connectivity between brain regions.” – Alice G. Walton
The higher centers of the human brain are contained in two separate hemispheres. Over evolutionary history these hemispheres have taken on different functions. For most people the left hemisphere has become responsible for language, mathematics, logic, and the activities of the right side of the body while the right hemisphere has become responsible for spatial ability, emotions, artistic expression, and the activities of the left side of the body. These differences in function are accompanied with differences in the sizes of the structures and their interconnectivity on the two sides.
Contemplative practices such as meditation, yoga, and tai chi have been shown to produce changes in the sizes, activity, and connectivity of brain structures through a process called neuroplasticity. The degree to which these practices might alter the differences between the hemispheres, however, has not been extensively studied. In today’s Research News article “Shifting brain asymmetry: the link between meditation and structural lateralization.” See:
or see summary below or view the full text of the study at:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4994843/
Kurth and colleagues investigate the effects of long-term meditation practices on the differences between the hemispheres. They recruited adult long-term meditators (> 4 years, mean 19 years of practice) and matched control subjects and subjected their brains to Magnetic Resonance Imaging (MRI) scans. These brain images were then analyzed for structural differences between the hemispheres.
They found that the meditators had larger parietal lobes and less difference between the two hemispheres than the non-meditators who had right hemispheres larger than the left. This difference was particularly centered in a parietal lobe structure called the precuneus. In addition, the greater the number of years of meditation practice, the larger the left hemisphere and the smaller the right hemisphere producing less of a difference between the sides. This decrease in the differences between the hemispheres was also present in the anterior cingulate cortex with the greater the number of practice years the smaller the differences.
These are interesting results that suggest that meditation practice reduces the differences between the hemispheres in the parietal lobe and anterior cingulate cortex. These areas are components of a neural system termed the Default Mode Network (DMN) which is activated during unfocused conscious activity deemed mind wandering. Meditation, with its emphasis on focused attention has been shown to reduce the size and connectivity of the DMN and mind wandering. Kurth and colleagues’ study suggests that meditation also reduces the differences in the sizes of the DMN in the two hemispheres.
These interesting findings suggest that long-term meditation practice may produce greater balance between the two hemispheres and this suggests greater intermixing of their separated functions; integrating the tow hemispheres’ functions. So, logical thinking and emotions intermix, art and language work together, the two sides of the body work more harmoniously and the individual attains a greater integrated wholeness. This is certainly one of the goals of meditation practice and the change in the hemispheric differences may signal success.
So, reduce brain asymmetries with meditation.
“The impact that mindfulness exerts on our brain is borne from routine: a slow, steady, and consistent reckoning of our realities, and the ability to take a step back, become more aware, more accepting, less judgmental, and less reactive. Just as playing the piano over and over again over time strengthens and supports brain networks involved with playing music, mindfulness over time can make the brain, and thus, us, more efficient regulators, with a penchant for pausing to respond to our worlds instead of mindlessly reacting.” – Jennifer Wolkin
CMCS – Center for Mindfulness and Contemplative Studies
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Study Summary
Kurth, F., MacKenzie-Graham, A., Toga, A. W., & Luders, E. (2015). Shifting brain asymmetry: the link between meditation and structural lateralization. Social Cognitive and Affective Neuroscience, 10(1), 55–61. http://doi.org/10.1093/scan/nsu029
Abstract
Previous studies have revealed an increased fractional anisotropy and greater thickness in the anterior parts of the corpus callosum in meditation practitioners compared with control subjects. Altered callosal features may be associated with an altered inter-hemispheric integration and the degree of brain asymmetry may also be shifted in meditation practitioners. Therefore, we investigated differences in gray matter asymmetry as well as correlations between gray matter asymmetry and years of meditation practice in 50 long-term meditators and 50 controls. We detected a decreased rightward asymmetry in the precuneus in meditators compared with controls. In addition, we observed that a stronger leftward asymmetry near the posterior intraparietal sulcus was positively associated with the number of meditation practice years. In a further exploratory analysis, we observed that a stronger rightward asymmetry in the pregenual cingulate cortex was negatively associated with the number of practice years. The group difference within the precuneus, as well as the positive correlations with meditation years in the pregenual cingulate cortex, suggests an adaptation of the default mode network in meditators. The positive correlation between meditation practice years and asymmetry near the posterior intraparietal sulcus may suggest that meditation is accompanied by changes in attention processing.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4994843/