Synchrony analysis of paroxysmal gamma waves in meditation EEG

Meditation is a fascinating topic that is still relatively poorly understood. To investigate its physiological traits, electroencephalograms (EEG) were recorded during meditation sessions. In a recent study, paroxysmal gamma waves (PGWs) have been discovered in EEG of meditators practicing Bhramari Pranayama (BhPr). In this paper, the synchrony between those PGWs is investigated, revealing functional connectivity patterns in the brain during BhPr. Specifically, the method “Stochastic Event Synchrony” (SES) is applied to pairs of PGW sequences in order to assess their synchrony. From those pairwise synchrony measures, large-scale functional connectivity patterns are extracted. Three subjects possessing different levels of expertise in BhPr are considered. Strong synchrony can be observed in the temporal lobes for all three subjects, in addition to long-range interhemispheric connections. Consistent connectivity patterns are present for exhalation periods of BhPr, while those patterns are substantially less stationary for inhalation periods. Interestingly, the synchrony seems to increase gradually during the meditation sessions. Moreover, the distribution of synchrony values seems to depend on the level of expertise in practicing BhPr: the higher the expertise, the more concentrated the intensity values.