EEG coherence increases between and within the cerebral hemispheres during Transcendental Meditation. EEG coherence is a quantitative index of the degree of long-range spatial ordering of the brain waves. The chart on the left shows that for a 2-week meditator, EEG coherence increased during the period of meditation. The chart on the right, of a 2-year meditator, shows high levels of coherence even before meditation began, spreading of coherence to high and lower frequencies about half way through the meditation period, and continuing high coherence even into the eyes-opened period after meditation.

Reference I: The Coherence Spectral Array (COSPAR) and its application to the study of spatial ordering in the EEG, Proceedings of the San Diego Biomedical Symposium 15: 1976. Reference II: Electrophysiologic characteristics of respiratory suspension periods occurring during the practice of the Transcendental Meditation program, Psychosomatic Medicine 46: 267-276, 1984.