Previously, the electroencephalogram (EEG) recorded while listening to repetition of a Sanskrit monosyllable (i.e., OM) was not significantly different from the EEG recorded during control periods. In the present study, fifteen adult volunteers from northern India (all male, average age 25.0 ± 4.9 years) were assessed using monopolar scalp EEG recordings before, during and after (i) silent repetition of a monosyllable (OM), (ii) silent repetition of 'one' and (iii) quiet rest. In (i), (ii) and (iii) breathing was not consciously modified. The participants had an average of five years' experience of focused meditation (dharana), involving awareness directed to the breath. Participants had no prior experience of silent repetition of either 'OM' or 'one'. They were Indian Hindus for whom OM has special spiritual significance, whereas 'one' does not. The sessions were on separate days in random order. The absolute and relative energy of theta waves in the EEG recorded at Pz-A2 increased significantly during repetition of OM compared to the preceding state. There were no changes during silent repetition of 'one' or during quiet rest. Increased energy in the theta band while awake reflects a state of relaxation devoid of effort. Hence, during silent repetition of OM alone there were changes suggestive of effortless relaxation.
Keywords: Electroencephalograph; Meditation; Silent repetition; Theta energy.
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