Enhanced EEG alpha time-domain phase synchrony during transcendental meditation: implications for cortical integration theory

Information transfer and integration in the brain that leads to high-level cognitive processes requires neuronal coordination. High phase synchronization (zero-lag) in fast frequencies is implicated in integrating sensory events. Alpha EEG activity, long regarded as a passive "idling" frequency, is now being implicated in this integrative function. As an example, in brain pathology decreased alpha phase synchrony is correlated with a decline in cognitive function. Transcendental Meditation (TM) provides an interesting starting point to study neuronal coordination because the "transcending" experience is a baseline state of consciousness, a condition of restful alertness without cognitive activity. Previous work on TM, reported to increase numerous indices of mind-body health, has been shown to increase neural coherence in the alpha band. In this study 15 subjects practicing the TM technique were investigated for changes in alpha phase synchrony. A time-domain method was used to measure millisecond phase shifts in 19 electrodes in long-term practitioners of TM in two conditions: eyes-closed resting and meditation. Significant reductions in millisecond phase lag were found during the meditation condition as compared to the eyes-closed resting condition in 30 of 49 long-range electrode pairings between frontal and occipito-parietal areas. Under the same conditions, twelve control subjects without meditation experience showed no change in alpha phase synchrony over the same time period. It is proposed that enhanced phase synchrony in the alpha frequency during meditation may improve functional integration and may have implications for performance and mind-body health. A short proposal for a phase synchrony model of consciousness is included.