Theta activity and meditative states: spectral changes during concentrative meditation

Abstract

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.

The exploration of meditation in the neuroscience of attention and consciousness

“…The research reports on meditation in this issue (Baerentsen et al 2010;Baijal and Srinivasan 2010;Cahn et al 2010;Travis et al 2010) investigate the neural changes as the practitioners meditate in the laboratory (Tagini and Raffone's article in this issue presents a related theoretical development). These studies employ both FA and OM meditation types.…”

“…For example, Baijal and Srinivasan (2010) recorded EEG during FA meditation and found increased theta activity in the frontal areas during the middle portion of the meditation period. With a completely different OM meditation (Vipassana), Cahn et al (2010) also found increase in theta activity in the frontal areas.…”

“…The studies also indicate differences in the rhythmic brain activity. For example, Baijal and Srinivasan (2010) found a decrease in theta activity in the parietal areas during the middle portion of the meditation period. Cahn et al (2010) found an increase in gamma activity in the parieto-occipital areas.…”

EEG Spectral Changes Before and After an Eight-week Intervention Period of Preksha Meditation

“…The most common findings in the studies of concentrative meditation showed an increase in theta band power (Baijal & Srinivasan, 2010). Theta band power and coherence was also observed in meditators performing Sahaj Yoga meditation as compared to non-meditators (Aftanas & Golocheikine, 2002).…”

“…This ACC is the main source of generation of theta rhythms (Gevins, Smith, McEvoy, & Yu, 1997). Also, the theta rhythm is considered as a monitor for focused attention and concentrative meditation (Baijal & Srinivasan, 2010) whereas the gamma rhythm helps in binding populations of neurons required for performing motor activity (Tallon-Baudry, Kreiter, & Bertrand, 1999).…”