AUTONOMIC CHANGES WHILE MENTALLY REPEATING TWO SYLLABLES - ONE MEANINGFUL AND THE OTHER NEUTRAL
Shirley Telles, R. Nagarathna and H. R. Nagendra Vivekananda Kendra Yoga Research Foundation, Bangalore, India. (Received on July 7, 1997)
Abstract: Autonomic and respiratory variables were recorded in 12 volunteers in three types of sessions (1) Before, during and after a test period of mentally repeating a meaningful syllable "OM" (MOM session),(2) A similar session except that the test period was spent mentally repeating a neutral word "one" (COM session), (3) A session with non-targeted thinking (NT session). The subjects were familiar with both syllables, and had been meditating on "OM" for 20 days. During the test periods of both MOM and COM sessions the rate of respiration (RR) and heart rate (HR) decreased significantly [two factor ANOVA (RR), paired t test (RR. HR)],compared to the pre period, mental repetition of "OM" (but not "one") caused a significant decrease in skin resistance level (SRL) (paired t test). This was taken to mean that the subject recognized the significance of the syllable. No significant change occurred during NT sessions.
Key words: relevant syllable; irrelevant syllable; skin resistance; breath rate; heart rate
INTRODUCTION The syllable "OM" is known to have profound significance in Indian culture. Mental repetition of this syllable was shown to cause significant changes in middle latency auditory evoked potentials, which were suggestive of a facilitation of neural activity at either mesencephalic or diencephalic level (1). In contrast mentally repeating a neutral syllable "one", inhibited neural activity at the same level. This was observed in subjects who had been regularly meditating on "OM" every day for more than 10 years ("experienced meditators"). In "naive" subjects, with 15 to 20 days of experience in meditation, repeating both "OM" and "one" caused the same effect, viz an inhibition of neural activity at mesencephalic or diencephalic level.
It was also reported that highly experienced meditators (20 years experience on an average) show a significant reduction in heart rate and a non significant trend of reduction in oxygen consumption while mentally repeating "OM" compared to a period of non targeted thinking (2). These subjects simultaneously displayed an increase in cutaneous vasoconstriction, which was interpreted as an increase in mental alertness (3), in the presence of other signs of reduced arousal (reduced heart rate and oxygen consumption).
The present study was conducted to compare the autonomic effects of mentally repeating a meaningful syllable with mental repetition of a neutral one and with non targeted thinking, in subjects who were acquainted with both syllables, and had been meditating on the meaningful syllable for 20 days, comparable to the naive subjects described earlier (1). The duration of meditation was believed to influence the ability to comprehend the significance of the syllable and a comparison with results obtained in experienced meditators, could be made.