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Brain oscillatory activity is associated with different cognitive processes and plays a critical role in meditation. In this study, we investigated the temporal dynamics of oscillatory changes during Sahaj Samadhi meditation (a concentrative form of meditation that is part of Sudarshan Kriya yoga). EEG was recorded during Sudarshan Kriya yoga meditation for meditators and relaxation for controls. Spectral and coherence analysis was performed for the whole duration as well as specific blocks extracted from the initial, middle, and end portions of Sahaj Samadhi meditation or relaxation. The generation of distinct meditative states of consciousness was marked by distinct changes in spectral powers especially enhanced theta band activity during deep meditation in the frontal areas. Meditators also exhibited increased theta coherence compared to controls. The emergence of the slow frequency waves in the attention-related frontal regions provides strong support to the existing claims of frontal theta in producing meditative states along with trait effects in attentional processing. Interestingly, increased frontal theta activity was accompanied reduced activity (deactivation) in parietal–occipital areas signifying reduction in processing associated with self, space and, time.
Transcendental Meditation (TM®) is derived from ancient yogic teachings. Both short- and long-term physiological correlates of TM® practice have been studied. EEG effects include increased alpha, theta, and gamma frequencies and increased coherence and synchrony. Neuronal hypersynchrony is also a cardinal feature of epilepsy, and subjective psychic symptoms, apnea, and myoclonic jerking are characteristic of both epileptic seizures and meditative states. Clinical vignettes have highlighted the potential risk of human kindling from repetitive meditation in persons practicing TM®, but clinical studies of similar techniques suggest that meditation may also be a potential antiepileptic therapy. Future clinical studies of meditating subjects using video/EEG monitoring are warranted to determine whether behavioral phenomena have an underlying epileptic basis, and prospective clinical trials of TM® in subjects with well-delineated epilepsy syndromes are necessary to establish the safety of this technique and its potential efficacy for seizure reduction and improvement of quality of life.