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Meditation and the EEG

Michael A. West

Psychological Medicine / Volume 10 / Issue 02 / May 1980, pp 369 ­ 375DOI: 10.1017/S0033291700044147, Published online: 09 July 2009

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How to cite this article:Michael A. West (1980). Meditation and the EEG. Psychological Medicine, 10, pp 369­375 doi:10.1017/S0033291700044147

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Psychological Medicine, 1980, 10, 369-375

Printed in Great Britain

Meditation and the EEGMICHAEL A. WEST1

From the Social Psychology Research Unit, University of Kent at Canterbury

SYNOPSIS Previous research on meditation and the EEG is described, and findings relating to EEGpatterns during meditation are discussed. Comparisons of meditation with other altered states arereviewed and it is concluded that, on the basis of existing EEG evidence, there is some reason fordifferentiating between meditation and drowsing. Research on alpha-blocking and habituation of theblocking response during meditation is reviewed, and the effects of meditation on EEG patternsoutside of meditation are described. In conclusion, the need for more precisely formulated research ispointed out.

INTRODUCTION

Over the last 10 years a great deal of researcheffort has been directed towards examining theeffects of the practice of meditation techniques.The research has examined changes taking placeboth during and outside of meditation practiceon psychophysiological and psychological param-eters. These results have suggested that de-creases in arousal occur during meditation andthat decreases in anxiety and neuroticism areassociated with learning and regularly practisinga meditation technique. Whether these resultsare due simply to placebo effects has not beenprecisely determined and there is still disagree-ment over the relative magnitude of the decreasesin arousal which are seen during meditation. Thegreatest research effort in the area, however, hasbeen in examining the EEG changes associatedwith meditation practice.

The earliest research interest in meditationcentred on the psychophysiological changeswhich occur during its practice (Das & Gastaut,1955; Bagchi & Wenger, 1957; Kasamatsu et al.1957), and these experiments examined the EEGchanges in some detail. Das & Gastaut (1955)reported that their 7 subjects (all Indian medi-tation experts) exhibited an increase in alphafrequency and a decrease in alpha amplitudecoupled with the appearance of generalized fastactivity during the ecstatic or 'samadhi' state.

1 Address for correspondence: Dr Michael A. West, SocialPsychology Research Unit, Beverley Farm, University ofKent, Canterbury, Kent.

Bagchi & Wenger (1975) took recordings from14 Indian Yogis who practised different tech-niques and took their equipment to both cavesand universities in order to contact expert practi-tioners of meditation. They found only thenormal alpha patterning between 8-5 and 11-5cps and no evidence of the high amplitude fastwaves reported by Das & Gastaut. It is interest-ing to note that the subjects of Das & Gastaut'swork reported entering the 'samadhi' (or ecstasy)state in meditation while those of Bagchi &Wenger did not, and this distinction of statesof meditation appears to be of importance inanalysing EEG findings. The techniques whichthe subjects in these 2 experiments practised,however, were diverse, and the experimenterscarried out different measurements on differentsubjects.

The first well controlled EEG study of medi-tation was conducted by Fenwick in 1960.Fenwick's subjects were Westerners who hadbeen taught a technique of mantra meditation(almost identical to Transcendental Meditationor 'TM'). The subjects were asked to meditatefor 30 minutes and to drowse for 30 minutes(randomized order of presentation). The recordsof 3 subjects were analysed and the author re-ported an increase in amplitude of alpha at thebeginning of meditation, accompanied later inmeditation by bursts of theta. Occasionallybursts of fast activity accompanied the theta.

In another careful study, Kasamatsu & Hirai(1966) selected 48 priests and disciples from theSotoandRinzai sects in Japan, whose meditation

3690033-2917/80/2828-4950 $01.00 © 1980 Cambridge University Press

370 M. A. West

experience ranged from 1 to more than 20 years.The EEG during Zazen (i.e. Zen meditationwhich involves the individual in sitting andmaintaining 'simply a quiet awareness, withoutcomment, of whatever happens to be here andnow' (Watts, 1962)) was characterized by theinitial appearance of 11-12 cps alpha, followedby an increase in alpha amplitude and a decreasein alpha frequency in the central and frontalregions. Occasionally, rhythmical theta trainsof 6-7 cps appeared. The authors found a directrelationship between the length of time theirsubjects had practised meditation and the natureof the EEG changes during meditation. Thosewith over 20 years' experience always exhibitedthe rhythmical theta trains. Twenty-four of thedisciples were evaluated by the Zen master onthe basis of'mental state', which was classified aslow, middle or high. The correlation of EEGchanges with 'mental states' was surprisinglyhigh, even higher in fact than the correlation withyears of meditation experience. Another interest-ing point to emerge from this study is that Zenmasters and disciples are capable of displayingEEG patterning normally associated with closedeyes in their Zazen (eyes open and focused)meditation.

In 1970, when Wallace published the results ofa study of the physiological effects of meditationon 15 subjects, his work received considerablepublicity. Among other psychophysiologicalchanges recorded during TM, he found that inthe EEG alpha amplitude increased and in4 subjects the alpha frequency slowed. In ' 2 or 3 'subjects the rhythmical theta trains reported byearlier workers were recorded. In a further study(Wallace et al. 1971), these findings were repli-cated more generally - the theta trains occurringin the records of 5 subjects. Banquet (1972,1973),in detailed examinations of the EEG changes inTM, observed a slowing of alpha frequency, anincrease in alpha amplitude and the occurrenceof the rhythmic theta trains. During 'transcend-ence ' (the deep stage of TM, presumably the sameas the samadhi or ecstasy stage), which was sig-nalled by the subject pressing a push button,patterns of generalized fast activity with a domi-nant beta rhythm around 20 cps were apparent.This latter finding replicated those of Das &Gastaut (1955) and Fen wick (1960), and suggeststhat this fast activity is characteristic of the 'deep'stages of meditation. Banquet found that the

beta rhythm stayed at an almost constant fre-quency during the transcendence stage. Fenwickhas replicated his and other researchers' findingsof increased alpha amplitude, decreased alphafrequency and the occurrence of theta activity(Fenwick et al. 1977). A summary of these find-ings reveals the following generally agreed EEGchanges during meditation:

(1) On beginning meditation alpha amplitudeincreases and in some cases alpha frequencyslows by 1-3 cps.

(2) Later in meditation trains of theta rhythmsoccur, often intermixed with alpha, especiallywhen the subject is experienced at meditation.

(3) During deep meditation, 'samadhi' or'transcendence', bursts of high frequency beta,20-30 or 40 cps can occur.

(4) At the end of meditation alpha sometimespersists even with eyes open.

In a more sophisticated examination of EEGchanges, Levine and colleagues (Levine, 1976;Levine et al. 1977) investigated the tendencytowards EEG coherence during meditation (pre-viously reported by Banquet, 1973), by determin-ing coherence bilaterally and homolaterallybetween central and frontal derivations of theEEG in a group of experienced meditators. Theyfound evidence of long range spatial orderingduring meditation which was not apparent in aneyes-closed relaxation period. This coherencewas particularly strong in the alpha and thetabands. The authors mention the possibility thattheir findings were due to arousal effects asso-ciated with the experimenter signalling the sub-jects to begin and end meditation. They dismissthis possibility as unlikely, despite Fenwicket fl/.'s (1977) finding that such arousal effects dooccur and can contribute in large part to apparentdecreases in arousal seen during meditation.This does not entirely account for the increase inalpha coherence observed during meditation,however, since in simple relaxation these patternsof change are not observed. In another study ofEEG coherence during meditation (Haynes et al.1977), consistency and spectral broadening ofalpha was found to be significantly correlatedwith clarity of 'transcendental' experiences,creativity and rapid neuromuscular recovery(H-reflex recovery). The authors somewhatimaginatively concluded that their results wereconsistent with the idea that 'coherent orderingof brain functioning during the Transcendental

Meditation and the EEG 371

Meditation technique provides a basis forcreative ability and holistic growth'.

Indeed, whether these EEG changes arecharacteristic of a unique 'wakeful hypometa-bolic physiologic state' (Wallace et al. 1971) hasbeen questioned by other researchers. In particu-lar, the similarity with self-hypnosis and lightsleep has been examined.

MEDITATION AND OTHER ALTEREDSTATES

In most studies of meditation, the meditationstate is compared with rest, napping or simplysitting with eyes closed. Tebecis (1975), however,compared the EEG during TM with the EEGduring self-hypnosis and found few compellingmean differences. TM subjects were comparedwith a passive control group and the data fromboth of these groups were contrasted with datafrom a group trained in self-hypnosis. (Theselatter data were taken from the results of aprevious experiment and it is not clear in theexperimental report how far the experimentalconditions were changed.) The self-hypnosisgroup had a significantly higher theta densitythan the TM group, who in turn displayed signi-ficantly more theta both in and out of meditationthan did the control group. It is difficult to extra-polate much from this study, since only a 2 minsample, 100 s into meditation, and a 100 s sampleprior to the end of meditation were taken. Never-theless, this experiment represents an attemptto compare meditation with another techniquewhich 'alters' consciousness, and a well-controlled exhaustive comparison of self-hyp-nosis and meditation would give more valuableinformation about the similarities and the diff-erences between these two techniques.

Drowsiness or light sleep has been proposed asa useful comparison condition for meditation,and a number of studies have attempted to makethis comparison (Fenwick, 1960; Otis, 1974;Banquet & Sailhan, 1974; Younger et al. 1975;Pagano et al. 1976). In Fenwick's (1960) com-parison of meditation and drowsiness, 3 EEGresearchers rated the records of 12 subjects byattempting to identify which represented drowsi-ness and which represented meditation. The mostexperienced rater achieved the best score - 10 outof 12 records being correctly identified. The least

24

experienced rater correctly identified 8 out of the12 records. Overall, the success rate was 27 cor-rectly identified records and 9 incorrectly identi-fied records. That these raters could achieve thissuccess rate argues that there are clear differencesbetween the EEG records of meditation anddrowsiness. The raters identified one of thesedifferences as the relative stability of the alpharhythm during meditation. In a subsequentexperiment (Fenwick et al. 1977), a consultantclinical neurophysiologist, when asked to allo-cate the EEG records of 24 subjects, correctlyidentified 13 meditation records and incorrectlyidentified 11 control records as meditation. Thisresult would have been expected by chance.

Banquet & Sailhan (1974) found significantdifferences in the amount of wakefulness(measured by the EEG) between the beginning ofmeditation and light sleep in a control group, andbetween the end of meditation and the end of aperiod of rest in a control group. Thus, the medi-tators appeared to remain wakeful during medi-tation, while the controls drifted towards sleepduring a comparable period of rest.

When the EEG records from meditation arescored by sleep researchers, a high percentage ofSleep Stage One is noted. Otis (1974) recordedthe EEG of 23 meditators and 21 controls (whoreceived no training) prior to the experimentalgroup learning meditation and again 3 monthsafterwards. In the post-treatment testing session,the TM group displayed significantly more SleepStage One activity during meditation than theyhad done in a pre-meditation rest period andsignificantly more than the controls. There wereno baseline differences between the groups priorto the experimental group learning meditation.

Younger et al. (1975) scored 31 meditationEEG records for sleep and found that 22-8 %

Table 1. Content of EEG records duringnapping and meditation

Sleep StagesWaking and Two, ThreeSleep Stage and Four

One(%) (%)Waking

MeditationNapping

59-529-4

•40-570-6

40017-5

Derived from the data of Pagano el al. (1976).Percentages represent time spent in different stages.

372 M. A. West

of the content of the records was Sleep StageOne, 17% was Sleep Stage Two and 59-63%was Wakefulness. Pagano et al. (1976) hadsimilar results when they compared the EEGsof meditation and 'napping' in 5 experiencedtranscendental meditators. They found ap-preciable amounts of Sleep Stages Two, Threeand Four during meditation, and questionedwhether the reported benefits of meditation weredue to the technique itself, since they mightpossibly be the results simply of sleep. Exami-nation of their data (Table 1) reveals significantdifferences between meditation and napping,however, and these results tend to confirm thefindings of Fenwick (1960) which suggested thatthe drowsiness state can be differentiated fromthe meditation state on the basis of EEG pat-terning. Fenwick et al. (1977) report that myo-clonic jerks observed during meditation aredifferent from those seen in normal drowsing,the former being repetitive, large, well-organizedbodily movements, usually confined to a limbor the trunk, whereas in drowsing the jerks areusually single, stereotyped and simple. A furtherdifference between meditation and the controlconditions in Fenwick's second study (Fenwicket al. 1977) is that 4 subjects displayed a signifi-cant increase in abnormal paroxysmal thetabursts during meditation. Similarly, Hebert &Lehmann (1977) found that 21 out of 78 ad-vanced practitioners of meditation demonstratedintermittent prominent bursts of frontally domi-nant theta activity. Subjects' reports suggestedthat these theta bursts were not related to sleep.During relaxation and sleep onset, 54 non-meditating controls showed no similar thetabursts. Hebert & Lehmann suggested that thesetheta bursts might be evidence of a stateadjustment mechanism that comes into playduring prolonged low-arousal states. Theyhypothesized that this mechanism might preventthe drift into sleep by widespread, brief, rhythmicneural activation.

Several authors have suggested on the basisof studies of the EEG that meditation is simplylight sleep by another name. Fenwick et al.(1977) point out that 'several subjects whoseEEG records showed them to be drowsy orfrankly asleep during the control periods did notrecognise this experience but insisted they hadbeen wide awake' and that 'it is predictable fromthe level of alertness seen in meditation that the

subject's self-report systems will not be function-ing effectively'. The implication of these state-ments is that the EEG is a more reliable indicatorof states of consciousness than is self-reportbut, as Fenwick goes on to point out, this maynot necessarily hold- ' Because the EEG phenom-ena are suggestive of a hypnagogic state it is notpossible to be sure that the mental state of stageonset sleep is present.' Indeed it is questionablewhether it is logical to score meditation recordsfor sleep stages and to call certain stages ofmeditation 'sleep' on the basis of EEG record-ings where there are consistent EEG differencesbetween meditation and 'napping' and whenmeditators consistently differentiate meditationsubjectively from drowsiness or sleep.

Thus, a number of researchers have shownEEG patterning similar to sleep stages duringmeditation, and subjective reports of meditators(West, 1980) imply the experience of somephenomena often associated with the hypnagogicstate. On the basis of existing research on theEEG and on other psychophysiological measurestaken during meditation (Woolfolk, 1975; West,1979a), it appears likely that meditation is,psychophysiologically, a finely held hypnagogicstate.

Williams & West (1975) compared 9 practis-ing meditators and 10 control subjects on theirEEG responses to photic stimulation. Onefinding from this study was that meditatorsshifted less along the arousal continuum than thecontrol subjects who tended to drift into sleep,suggesting that meditation practice may pro-duce an ability to hold the hypnagogic state. It isof interest also that regular meditators, deprivedof sleep, show significantly less compensatoryparadoxical sleep than non-meditators after aperiod of sleep deprivation, and that their returnto pre-deprivation levels of paradoxical sleep issignificantly faster than that of control subjects(Miskiman, 1977). Woolfolk et al. (1976) havealso reported that meditation is an effectivetreatment for chronic insomnia.

ALPHA-BLOCKING AND HABITUATIONOF THE BLOCKING RESPONSE INMEDITATION

Das & Gastaut (1955) report no effect on theEEG pattern as a result of external stimuli duringthe ecstasy stage of meditation. Similarly,

Meditation and the EEG 373

Bagchi & Wenger (1957) found that 'low inten-sity noise' i.e. shuffling of feet, produced noalpha-blocking in one subject. Kasamatsu et al.(1957) found that the alpha waves of theirmeditating subjects 'were hardly depressed bythe sound of hand claps and bells'.

In a more systematic study of alpha-blockingand habituation, Kasamatsu & Hirai (1966) pre-sented a click stimulus every 15 s to a group ofZen masters in Zazen meditation and found noevidence of habituation. A control group ex-hibited the classical habituation curve to thesame stimulus during a period when they satquietly with eyes open. The Zen masters arereported to have displayed 'theta blocking' tothe click stimulus. When the stimulus was pre-sented during a train of theta, the theta wasblocked, not being replaced by alpha - theusual arousal reaction in drowsiness - but re-turning within a few seconds. Banquet (1973)has also reported this phenomenon in TM sub-jects.

Wallace (1970) and Wallace et al. (1971) re-ported no habituation of the blocking responsein meditating subjects. Banquet (1973), however,reports that with TM subjects there was 'usuallyno blocking', though click stimulation of thetadid produce a blocking effect as reported above.In deep meditation, Banquet found that therewas no change in the electrical pattern as a resultof stimulation. Anand et al. (1961) also reportthat during 'samadhi' there was no blocking.

These conflicting results must derive at leastpartially from the fact that different experi-menters have used subjects with vastly differentexperience of meditation and who employ dif-ferent techniques of meditation. It seems pos-sible from an examination of the literature thatthere is no habituation of the blocking responsein experienced meditators and that there is astage of 'deep' meditation (with a variety ofnames such as samadhi or transcendence) wherethe alpha-blocking response does not occur.Unfortunately, too few systematic studies ofalpha-blocking and its habituation which haveused meditators as subjects have been conducted.

THE EEG BEFORE AND AFTERMEDITATION

Schwartz (1973) reports that meditators showmore alpha with eyes open upon entering the

laboratory than controls, yet after brief medi-tation this was reversed. Kras (1977) found thatmeditators displayed significantly more alphathan controls in eyes-open and eyes-closed con-ditions. Tebecis (1975) found that meditatorsexhibited a higher theta density out of medi-tation than controls, though he found no evi-dence of differences on the alpha range. A num-ber of researchers have reported that alpha per-sists after meditation, even with eyes open (Das&Gastaut, 1955; Hirai et al. 1959; Hirai, 1960;Kasamatsu & Hirai, 1966; Wallace, 1970;Banquet, 1973). Westcott (1977) compared inter-hemispheric EEG symmetry in a group of medi-tators and 2 control groups. Between-groupdifferences showed that the EEG was correlatedmore highly across hemispheres in the medi-tating group than in the control groups, over thealpha range. This was true before, during andafter a period of meditation (during which thecontrols either relaxed or concentrated on aletter writing task). The meditators also dis-played a lower right to left hemisphere powerratio than the other two groups, thus providingsome support for Ornstein's (1972) suggestionthat meditation practice may produce a greaterintegration of hemispheric functioning.

In a longitudinal study of a group of subjectswho learned meditation, subsequent to an initiallaboratory testing session (Vassiliadis, 1973),significant changes were seen in alpha and thetacontent in the occipital region as a function oflength of practice. After 6-9 months of medi-tation, the meditators showed more alpha con-tent than a control group, when sitting witheyes open. Following a 20 min period of medi-tation, the alpha content in the post-meditation,eyes-open period was significantly greater thanpre-meditation levels. After 6-9 months ofmeditation, there was a significant gradual in-crease in theta wave power during meditationand the theta content was higher at the end thanat the beginning of meditation. In another longi-tudinal study of the effects of meditation, Glueck& Stroebel (1975) taught a group of in-patientsin a psychiatric hospital a technique of medi-tation. Over a 6-month experimental period thepatients exhibited a significant increase in restingdensity of alpha outside of meditation and anincrease in density of alpha during meditation.A control group exhibited no significant change.

In a study of EEG responses to photic stimu-24-2

374 M. A. West

lation in meditators (Williams & West, 1975), itwas found that meditators exhibited the alphainduction response earlier than a control group,and the incidence of the alpha induction responsewas significantly higher among the meditators.One interpretation offered for this latter findingwas that the regulation of attention duringmeditation may have led to an increased abilityin the meditators to sustain attention. Recentresearch has shown that there are reliable in-creases in measures of attentional absorption inconjunction with a significant decrement in traitanxiety, as a function of length of time of practiceof meditation (Davidson et al. 1976), thoughwhether these increases in absorption are due todecreases in anxiety or attentional regulationdirectly produced by meditation has not yet beendiscovered.

CONCLUSIONS

Research into meditation suggests that medi-tation is associated with increases in subjectivefeelings of relaxation and decreases in measuredanxiety (West, 1980; Hjelle, 1974; Fehr, 1977).Meditation has been used successfully as atherapy in cases of insomnia (Woolfolk et al.1976), hypertension (Patel, 1977), and headache(Benson et al. 1974). How meditation achievesits effects and whether they are primarily due toplacebo effects, experimenter effects and cognitivedissonance effects, is open to debate. Researchon psychophysiological correlates of meditationhas shown that decreases in arousal take placeduring meditation (Woolfolk, 1975), and possiblyoutside of meditation, as a result of regularpractice (West, 19796; Goleman & Schwartz,1976), though there is some disagreement aboutthe relative magnitude of these effects (Fenwicket al. 1977). The work on meditation and theEEG has produced results which suggest thatmeditation might be differentiated from otheraltered states and is therefore of some importance.Future research might answer some of thequestions posed or rebuff suggestions made inthis review, but there is obviously a need forbetter-controlled and more precisely formulatedresearch, since meditation is increasingly beingused as a form of therapy (Shafii, 1973;Carrington, 1977) and may represent a method ofproducing generalized relaxation and relieffrom anxiety and tension. Akers et al. (1977), in

an investigation of personality correlates of EEGresponses to meditation, have found that thoseindividuals who indicated more concern withtheir physical or psychological well-being alsoexhibit a greater psychophysiological response(in terms of increased alpha) to meditation thanthose who indicated less concern. These findingsare consistent with other research which hasshown that those attracted to meditation aresignificantly more neurotic than the normalpopulation (West, 1980). Thus, it may be pos-sible to predict, on the basis of EEG responses tomeditation, which individuals would be mostlikely to derive therapeutic benefit from con-tinued meditation practice. The possible use-fulness of the EEG as the most reliable psycho-physiological measure of both the response tomeditation, and the effectiveness of meditationin producing relaxation over time, is thereforeapparent.

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