Frontal brain coherence, but not lateral asymmetry, increases with long-term Transcendental Meditation practice. In two studies, frontal coherence was higher in 13 TM practitioners than in 12 controls, and in a one-year longitudinal study of 14 participants, coherence increased linearly during computer tasks and eyes-closed rest, and rose to a high level after 2 months of TM practice. Lateral asymmetry did not change in any condition. Coherence was more sensitive than lateral asymmetry to the effects of TM practice on brain functioning.
EEG alpha coherence and slow alpha power were recorded from frontal and occipital derivations during relaxation or the Transcendental Meditation (TM) technique in fifteen subjects. Subjects were tested before and after a two-week baseline period in which half practiced twice daily relaxation and half did not change their schedule. All subjects were then instructed in the TM technique and retested after a two-week period of twice daily practice of the technique. During the first two-week period there were no group differences or group by session interactions, but there was a significant effect of repeated measurement, indicating a decrease in occipital power independent of group.