Electroencephalographic findings during mantra meditation (transcendental meditation). A controlled, quantitative study of experienced meditators

The EEGs of 13 experienced practitioners of transcendental meditation (TM) were recorded for 5 min preceding TM, during 20 min of TM and until 5 min after, as well as during closed-eyed wakefulness, drowsiness, sleep onset and sleep. Thirteen healthy volunteers matched for age served as control subjects. Computer period-amplitude analysis of F3-C3, T3-T5, P3-O1, F4-C4 and P4-O2 epochs of 50--100 sec duration resulted in a frequency and amplitude spectrum (0.5--28.6 c/sec), and the mean frequency and the mean voltage of each EEG lead. The EEG frequency spectra constituted a continuum with increasing theta and delta activity and decreasing alpha activity as the participants tended to fall asleep. The frequency spectrum during TM corresponded to a spectrum situated between that of wakefulness and drowsiness and remained virtually unchanged during the 20 min of meditation. The EEG mean frequency of the TM group was about 1 c/sec slower than that of the control group. Intra- or interhemispheric differences between quantities of EEG activity remained stable during TM, nor did we observe any theta bursts. There was no consistent EEG patter associated with a successful or unsuccessful meditation, nor did the EEGs of two meditators who stated they had felt drowsy during TM show a different pattern.