Indian J Physiol Pharmacol 1995; 39(4): 418-420

SHORT COMMUNICATION

AUTONOMIC CHANGES DURING "OM" MEDITATIONSHIRLEY TELLES*, R. NAGARATHNAAND H. R. NAGENDRA

Vivekananda Kendra Yoga Research Foundation,Bangalore - 560 018

( Received on July 19, 1994 )

Abstract: The autonomic and respiratory variables were studied in sevenexperienced meditators (with experience ranging from 5 to 20 years). Eachsubject was studied in two types of sessions - meditation (with a period ofmental chanting of "OM")and control (with a period of non-targetted thinking).The meditators showed a statistically significant reduction in heart rate duringmeditation compared to the control period (paired 't' test). During both typesof sessions there was a comparable increase in the cutaneous peripheralvascular resistance. Keeping in mind similar results of other authors, this wasinterpreted as a sign of increased mental alertness, even while beingphysiologically relaxed (as shown by the reduced heart rate).

Key words: oxygen consumptionmetabolism

INTRODUCTION

Mentally chanting "OM" was shown toincrease the efficiency with which sensoryinformation was processed in subjects with morethan 10 years ofmeditation experience, whereasmentally chanting "one" had the opposite effect(1). These changes occurred mainly at themesencephalic or diencephalic level. Anotherstudy of 7 proficient subjects (3 of whom had 20years experience of meditation), revealed thatmental chanting of "OM"activated higher neuralcentres, i.e. the association cortices (2). Mentalchanting of "OM" leads to a single thoughtstate, and a subjective feeling of deep relaxation.Hence the present study was carried out to findout whether "OM"meditation would also causechanges in the autonomic and metabolicfunctions of the seven experienced meditatorswhose neural responses to the meditation weredescribed above (2).

METHODS

Subjects,' The study was carried' out on 7normal, healthy male volunteers in the agerange of 29 to 55 years (mean ± SD, 42.3 ± 9.8years). They were all committed meditators withexperience ranging between 5 and 20 years. The

yogameditation

details of the study were explained to thesubjects and their signed informed consent wastaken in accord with the ethical guidelines ofthe Indian Council of Medical Research, NewDelhi.

Design of the study,' Each session was of 32min duration, of which 20 min were spent inmeditation, preceded and followed by two 6 minperiods of sitting relaxed, with eyes closed.Subjects were also studied in control sessionswhich were of the same duration as themeditation sessions, and similar in design exceptthat the 20 min period was spent sitting relaxedwith eyes closed, and non-targetted thinking(instead of meditation). Meditation involvedmental chanting of "OM", while sittingcomfortably, with eyes closed. Both types ofsessions were repeated on three separate days.

Parameters studied,' Recordings of autonomicand respiratory variables were made on a 10channel polygraph (MadeIIO, Polyrite, Recordersand Medicare systems, Chandigarh, India). EKGwas recorded using the standard limb lead Iconfiguration. Heart rate was obtained bycounting the number of QRS complexes per 40see intervals continuously. Epochs of 40 seewere chosen to be able to correlate this data

*Corresponding Author

Indian J Physiol Pharmacol 1995; 39(4)

with that of subjects practicing other meditations(3). This has been described in the discussion.Palmar skin resistance (SR) was recorded using2 silver chloride disc electrodes filled withelectode jelly (CSR Technocarta, Hyderabad,India), placed 4 em apart on the palmar surfaceof the right hand. SR values were sampledcontinuously at 20 see intervals. Skin blood flowwas recorded using a photo-electricplethysmograph placed over the left thumb nail.The amplitude of six plethysmogram waveformswere calculated in each minute. Two nasalthermistors placed one at each nostril wereused to record respiration. The number of breathcycles in each minute was calculated to give therespiratory rate. Oxygen consumption wasrecorded using the closed circuit Benedict-Rothapparatus. In this method, the subject breathedinto an oxygen tank wearing a close fittingmask, and with a nose clip. The exhaled carbondioxide does not enter the tank, as it is absorbedby soda lime. The difference between the initialand final volumes of oxygen in the tank is theamount of oxygen consumed by the subject in agiven period of breathing (i.e. 5 min). Therecording laboratory had a temperature of 25 ±1°C, with relative humidity about 70 percent.

Autonomic Changes during Meditation 419

The values were corrected for standardtemperature and pressure.

The OC recordings were made before andafter meditation, but not during meditation.Polygraphic recordings were made before,during, and after meditation.

Values of the 5 variables mentioned abovewere averaged for each of the 3 periods of asession viz. before, during and after meditation(or the control procedure). Statistical analysis ofthese averaged values was done to revealsignificant differences between (a) before versusduring meditation (or control) and (b) duringmeditation versus during control periods, usingthe paired 't' test.

RESULTS

All seven meditators showed a small butstatistically significant reduction in heart rateduring meditation compared to the control period(P<O.OOl,paired 't' test, Table D. There was asignificant and comparable decrease in fingerplethysmogram amplitude, during the meditationand control periods compared to the precedingperiods (P<0.05, paired 't' test, in both cases).There was also a non-significant trend of

TABLE I: Autonomic and respiratory variables recorded in 7 meditators. Values are Group mean ± S.D.

Variables studiedI

Meditation session Control session

Pre During Pre During

Heart rate 47.00 46.90** 47.20 47.60(Beats per 40 see) ±5.00 ±4.30 ±4.90 ±4.80

Respiratory rate 10.80 10.40 10.50 11.10(Breaths per min) ±3.60 ±3.30 ±3.40 ±3.20

Skin resistance 412.90 446.60 307.40 335.70(Kilo ohms) ±129.90 ±107.10 ±123.40 ±113.80

Finger plethysmogram 1.00 0.70* 1.10 0.70#amplitude (rnm) ±0.20 ±0.20 0.20 ±0.20

Oxygen Consumption was recorded immediately before and after the meditation period, but not during.

Oxygen consumption Pre Post Pre Post

(ml/min STPD) 454.00 386.20 480.30 483.80±192.00 ±68.70 ±153.00 ±232.50

** P<O.OOl,during meditation versus during control (paired 't' test).it P<O.05, before versus during period (paired 't' test).

420 Telles et al

reduction in the oxygen consumption followingmeditation (P>O.05, paired 't' test). The groupaverage values ± SD for all 5 variables are asshown in Table I.

DISCUSSION

The present study revealed a significantdecrease in heart rate during mental chantingof -"OM", which is suggestive ofpsychophysiological relaxation. The non-significant trend of reduction in oxygenconsumption also has a similar interpretation.This change is similar to that caused by TM (4),though of smaller magnitude.

However, it is important to note that theactual pre-meditation (or control) values ofoxygen consumption of the (senior) meditatorsof the present study were noticeably higherthan those of other meditators (4), and of thegeneral population. Since it is usually thoughtthat yoga practitioners have lower oxygenconsumption values than those who do notpractise yoga, these results are difficult toexplain. There is a report (5) in the literaturewhich demonstrated an increase in the basalmetabolic rate (BMR) with six weeksexperience in yoga, compared to the period beforelearning yoga. The BMR decreased, but did notreturn to the initial value after continuing yogapractice for six weeks. In contrast to the presentstudy, the subjects were not practisingmeditation, but were practising specific postures(yogasanas) and breath regulation (pranayama).Hence no direct correlation can be made between

Indian J Physiol Pharmacol 1995; 39(4)

the two studies, and further assessments arenecessary to come to a definite conclusion.

The significant decrease in fingerplethysmogram amplitude (i.e. increasedperipheral vascular resistance) which occurredduring both meditation and control periods is asign of increased sympathetic tone and hence isalso not expected during meditation (4).

While attempting to explain these seeminglycontradictory results, it is to be noted that thesame individual may simultaneously showchanges in two variables indicating oppositestates of arousal, e.g. a decrease in heart ratealong with reduced skin resistance. Whileexplaining similar contradictory changes inAnanda Marga meditators (6), the authorsdescribed the reduced skin resistance as anattempt to prevent intrusion of sleep during thesession. Since reduced skin blood flow is knowto occur when the subject is alert, as whilesolving arithmetic problems mentally (7), thepresent study might indicate that chanting "OM"mentally causes increased alertness (reducedfinger plethysmogram amplitude), even thoughthe subject was more relaxed (reduced heartrate).

ACKNOWLEDGEMENTS

This study was designed and carried outunder the expert guidance of (the late) Dr. T.Desiraju (NIMHANS, Bangalore). Thecontributions of the other staff of "ProjectConsciousness", are gratefully acknowledged.

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Alterations in auditory middle latency evokedpotentials during meditation on a meaningful symbol-"OM". Int J Neurosci 1994; 74:87-94.

2. Telles S, Desiraju T. Recording of auditory middlelatency evoked potentials during the practice ofmeditation with the syllable "OM". Indian J Med Res1993; [B] 98:237-239.

3. Telles S, Desiraju T. Autonomic changes inBramakumaris Raja Yoga Meditation. Int JPsychophysiol 1993; 1:147-152.

4. Wallace RK, Benson H, Wilson AF. A wakefulhypometabolic physiologic state. Am J Physiol 1971;221:795-799.

5. Dhanaraj YH. the effects of yoga and the 5BXfitness plan on selected physiologic parameters.In Science studies Yoga. FunderburkeJ (Ed), Illinois, Himalayan InternationalInstitute, 1977.

6. Corby JC, Roth WT, Zarcone YP, Kopell BS.Psychophysiological correlates of the practice ofTantric Yoga meditation. Arch Gen Psych 1978; 36:571-577.

7. Delius W, Kellerova E. Reaction of arterial andvenous vessels in the human forearm and hand todeep breath or mental strain. Clin Sci 1971; 40:271-282.