Theta activity and meditative states: spectral changes duringconcentrative meditation

摘要

Brain oscillatory activity is associated withdifferent cognitive processes and plays a critical role inmeditation. In this study, we investigated the temporaldynamics of oscillatory changes during Sahaj Samadhimeditation (a concentrative form of meditation that is partof Sudarshan Kriya yoga). EEG was recorded during Su-darshan Kriya yoga meditation for meditators and relaxa-tion for controls. Spectral and coherence analysis wasperformed for the whole duration as well as specific blocksextracted from the initial, middle, and end portions of SahajSamadhi meditation or relaxation. The generation of dis-tinct meditative states of consciousness was marked bydistinct changes in spectral powers especially enhancedtheta band activity during deep meditation in the frontalareas. Meditators also exhibited increased theta coherencecompared to controls. The emergence of the slow fre-quency waves in the attention-related frontal regions pro-vides strong support to the existing claims of frontal thetain producing meditative states along with trait effects inattentional processing. Interestingly, increased frontal thetaactivity was accompanied reduced activity (deactivation) inparietal—occipital areas signifying reduction in processingassociated with self, space and, time.