Short-term longitudinal effects of the transcendental meditation technique on EEG power and coherence.

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. After the two-week TM technique period, subjects showed a significant increase in frontal alpha coherence above a 0.95 threshold. Frontal alpha coherence was found to be a more sensitive discriminator of the TM technique than alpha power, which may clarify previously reported nonsignificant EEG differences between the TM technique and general relaxation.