Comparative EEG analysis of Sutra and Tantra meditations: insights into meditative states and long-term traits
چکیده
Introduction The Tibetan Buddhist tradition distinguishes between two broad categories of meditation: Sutra and Tantra, which differ in the methods and mental faculties they employ. The main neurophysiological studies of Tibetan Buddhist meditation have been conducted mostly on Sutra practices; while Tantric meditation remains less studied. Methods This publication presents a dual comparative study, using both between-groups and within-subjects design, of the neurophysiological (EEG) correlates characterizing Sutra and Tantra meditative practices, examining both the meditative states and the meditative traits. The study was carried out within the natural environment of Tibetan Buddhist monasteries in India, maintaining the socio-cultural context. Two groups of long-term practitioners (Buddhist monks of Gelug lineage), one experienced in the Tantra tradition (T-group, n = 21) and the other in the Sutra tradition (S-group, n = 20) participated in the study. Results A between-group cluster permutation test revealed that the groups differed in EEG alpha power during meditation, as well as in baseline resting conditions before and after meditation. Specifically, T-group demonstrated consistently lower alpha power compared to the S-group, regardless of the conditions. Thus, the observed differences are stable characteristics of the groups. The within-subjects analysis demonstrated that the conditions (meditation, and baseline resting states before and after meditation) differed only in the T-group: during meditation, an increase in individual alpha peak frequency (iAPF) was observed in the occipital leads, followed by a decrease in iAPF after meditation. Discussion We suggest that reported between-group differences represent enduring meditative traits developed through years of training in meditative techniques in the Sutra and Tantra traditions. Nevertheless, we cannot entirely exclude the possibility that these variations may also stem from certain cohort-specific characteristics unrelated to meditation. An examination of individual power spectra revealed that the absence of significant differences in EEG spectral power between conditions can be primarily attributed to the inter-individual variability in both groups. This variability, in turn, may stem from extensive expertise of highly experienced practitioners, who over years of training, develop individualized cognitive strategies for maintaining the meditative state. Our future research will focus on a more detailed quantitative analysis of inter-individual variability during meditations and on identifying additional between-group differences among practitioners in different traditions.