Neuroimaging Research on Yoga and Meditation: EEG Studies

Nikhil Ramburn and Sat Bir Singh Khalsa, Ph.D.

Historical anecdotal evidence abounds for the benefits of yoga and meditation and even for the underlying psychophysiological and psychological mechanisms of its action. Since the history of the practice goes back thousands of years, the writings of the yoga and meditation masters over the millennia have given us valuable insight into how meditation works. However, anecdotal evidence can be very subjective and may not apply to the general population. Therefore, more objective studies have tried to quantify the effects of meditation and the neurophysiological processes involved. One of the early scientific tools used to study the contemplative practices has been electroencephalography (EEG). The EEG records the electrical activity of the brain with electrodes on the surface of the scalp and registers the distinctly different brain wave patterns that occur over different regions of the scalp and that change their characteristics over time and with different meditation practices.

EEG research has revealed that yoga has positive and unique effects on brain activity by stimulating alpha, beta, and theta brainwaves. These changes in brain activity have been associated with improvements in cognition, mood, and anxiety. Alpha brainwave activity has been correlated with increased cognitive performance such as faster recall of information from memory. Likewise, beta waves have been linked to increased cognitive skills, which are associated with improved academic performance and mood. Those beneficial brain wave activities were observed in the various EEG studies on yoga practitioners.

The first EEG studies from the early sixties and seventies revealed increases in alpha and theta wave amplitude in yoga practitioners. Later studies were consistent with these findings, such as in a 1992 Indian EEG study, in which a breathing and relaxation yoga practice was equated with gradual and significant increases in alpha activity over 30 consecutive days of training. Those increases in alpha activity were registered in the occipital and prefrontal cortices of the brain. Scientists have found an integral link between the prefrontal cortex and the personality. This finding is consistent with Yogi Bhajan’s description of the frontal lobe of the brain as the control center for the personality and several meditations in the Kundalini Yoga tradition target this brain area.

In another more recent study from 2013, a group of Indian police trainees performed asana-based yoga and pranayama. Just as in the previous study, these subjects also displayed increase in alpha wave activity along with amplification of beta brainwaves. Several more EEG studies have demonstrated that a natural practice like yoga can induce brain wave activity associated with a vast array of cognitive and mood benefits. Therefore, the EEG studies have been instrumental in initiating our understanding of the yogi’s meditative mind.
The recent advent of the popularity of Buddhist inspired mindfulness meditation has yielded an additional body of research literature on its EEG characteristics. In a recent review of EEG studies on mindfulness meditation published in a 2015 issue of the journal Neuroscience and Biobehavioral Reviews by a team of U.K. researchers, the authors examined 56 publications. They concluded “that mindfulness was most commonly associated with enhanced alpha and theta power as compared to an eyes closed resting state, although such outcomes were not uniformly reported. No consistent patterns were observed with respect to beta, delta and gamma bandwidths.” This conclusion is in essence not much different from previous meditation studies, in which a single point, or closed focus, form of meditation has been used. The fact that the EEG is not able to show substantial differences between meditation forms may suggest that it has significant limitations.

Despite its benefits, the capability of EEG recordings may not do full justice as a tool to evaluate the subtlety of meditative practices and experience. This technology has the limitation of representing the activity of millions of neurons through interpreting brain wave activity alone. Another major limitation to the EEG is its poor spatial resolution since it is most sensitive to the neural activity in the superficial layers of the brain, because the scalp electrodes are a significant distance away from the neurons through the barriers of the skull and scalp. Deeper structures in the brain that are further from the scalp electrodes such as the cingulate gyrus or hippocampus have less contribution to the EEG signal. While the early neuroimaging studies have yielded valuable information about the effects of yoga on brain activity, the limitations of the EEG technology have restricted what we can learn from these studies. There is now new neuroimaging technology that offers measurements that are free of the many artifacts and limitations of the EEG.
Nikhil Rayburn grew up practicing yoga under mango trees in the tropics. He is a certified Kundalini Yoga teacher and has taught yoga to children and adults in Vermont, New Mexico, Connecticut, India, France, and Mauritius. He is a regular contributor to the Kundalini Research Institute newsletter and explores current yoga research.
Sat Bir Singh Khalsa, Ph.D. is the KRI Director of Research, Research Director for the Kripalu Center for Yoga & Health, and Assistant Professor of Medicine at Harvard Medical School. He has practiced a Kundalini Yoga lifestyle since 1973 and is a KRI certified Kundalini Yoga instructor. He has conducted research on yoga for insomnia, stress, anxiety disorders, and yoga in public schools, he is editor in chief of the International Journal of Yoga Therapy and The Principles and Practice of Yoga in Health Care and author of the Harvard Medical School ebook Your Brain on Yoga.

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