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Chapter 2:
Physiological Effects
The Cortical System
EEG: Alpha Activity
Evidence indicating that meditation leads to an increase in alpha rhythms (slow, high amplitude brain waves extending to anterior channels and ranging in frequency from eight to thirteen cycles per second) is extensive. The following studies, using many types of meditation, with subject groups of one to more than fifty including beginners and Zen masters, reach that conclusion: Delmonte (1984f), Daniels and Fernhall (1984), Stigsby et al. (1981), Lehrer et al. (1980), Wachsmuth et al. (1980), West (1980a), Dostalek et al. (1979), Corby et al. (1978), Pelletier and Peper (1977b), Elson et al. (1977), Kasamatsu et al. (1957), Kras (1977), Fenwick et al. (1977), Glueck and Stroebel (1975), Tebecis (1975), Williams and West (1975), Woolfolk (1975), Banquet (1972, 1973), Vassiliadis (1973), Benson et al. (1971c), Wallace et al. (1971c), Akishige (1970), Wallace (1970), Kasamatsu and Hirai (1963, 1966, 1969a, 1969b), Kamiya (1968, 1969b), Anand et al. (1961a), Hirai (1960), Hirai (1959), Bagchi and Wenger (1957), and Das and Gastaut (1955) [see also the EEG research review of Echenhofer and Coombs (1987)].
In contrast, some studies report a decrease in alpha activity during meditation. See Jacobs and Luber (1989), Warrenburg et al. (1980), and Tebecis (1975). A possible explanation may be found in differences in the initial level of relaxation of subjects.
Gayten (1978) examined the EEGs of tai chi practitioners (a form of moving meditation) using a Medi-Log Ambulatory Monitor and did not find brain-wave patterns similar to those of meditators. After reviewing their own and other studies, Jevning and O'Halloran (1984) concluded that various TM-correlated changes persisted after the cessation of TM practice, particularly EEG changes of the kind reported in the studies we have listed here.
Sim and Tsoi (1992) investigated the effects of three centrally acting drugs (naloxone, diazepam, and flumazenil) on the significant increase in the intermediate alpha frequency of the EEG that accompanied meditation in an experienced meditator. They found no significant changes, which would indicate that the EEG correlates of meditation are not causally related to the rise or fall of endogenous opioid peptides or benzodiazepinelike substances in the brain.
EEG: Theta Activity
A characteristic brainwave pattern of long-term meditators includes strong bursts of frontally dominant theta rhythms (five to seven cycles per second), during which meditators report peaceful, drifting, and generally pleasant experiences with intact self-awareness. The following studies have reported this pattern: Jacobs and Luber (1989), Delmonte (1984f), West (1979a), Hebert and Lehmann (1977), Elson et al. (1977), Pelletier and Peper (1977b), Fenwick et al. (1977), Banquet and Sailhan (1977), Ghista et al. (1976), Levine (1976), Tebecis (1975), Glueck and Stroebel (1984), Krahne and Tenoli (1975), Hirai (1974), Banquet (1972, 1973), Wallace and Benson (1972), Wallace et al. (1971b), Wallace (1971), Kasamatsu and Hirai (1963, 1966), Anand et al. (1961b), and Bagchi and Wenger (1958).
EEG: Beta Activity
During deep meditation, experienced subjects sometimes exhibit bursts of high-frequency beta waves (twenty to forty cycles per second). This sudden autonomic activation is often associated by the meditator with an approach of yogic ecstasy or a state of intense concentration; and it is usually accompanied by an acceleration of heart rate. The following studies have reported beta activity: West (1980a, Peper and Ancoli (1979), West (1979a, Corby et al. (1978), Fenwick et al. (1977), Banquet (1973), Kasamatsu and Hirai (1963, 1966), Anand et al. (1961a), and Das and Gastaut (1955). Surwillo and Hobson (1978) recorded the EEGs of six Protestant adults during prayer to discover whether the pattern was slower than during rest. They did not find any evidence of EEGs slowing during prayer, and in fact found the opposite in the majority of subjects. The authors speculated that this phenomenon was similar to that observed in experienced meditators during deep meditation.
EEG: Hemispheric Synchronization
EEG synchronization/coherence with respect to the distribution of alpha activity between the four anatomically distinct regions of the brain—-left, right, anterior, and posterior—-may indicate the effectiveness of meditation. It has been positively correlated with creativity (Orme-Johnson et al. 1977b). Such neural ordering has been reported in the following studies: Jevning and O'Halloran (1984), Badawi et al. (1984), Orme-Johnson and Haynes (1981), Dillbeck and Bronson (1981), Dillbeck et al. (1981a), Glueck and Stroebel (1978), Corby et al. (1978), Bennett and Trinder (1977), Orme-Johnson (1977a), Morse et al. (1977), Hebert and Lehmann (1977), Westcott (1977), Haynes et al. (1977), Ferguson and Gowan (1976), Davidson (1976), Levine (1976), Ferguson (1975), Glueck and Stroebel (1975), Banquet and Sailhan (1974), Banquet (1973 and 1972), Wallace et al. (1971c), Wallace (1971), Anand et al. 1961a), and Das and Gastaut (1955).
EEG: Dehabituation
Whether meditation produces a heightened awareness that resists habituation is a significant question, we feel, because many traditional teachings maintain that it does. The Sanskrit anuraga, or constant freshness of perception, for example, is said to be a primary result of yoga; Zen Buddhist teachers describe the freedom from "perceptual averaging" that zazen and right living lead to; and Taoist stories accentuate the spontaneity of each moment for those who are wise in the way of the Tao. Such teachings are supported by most modern meditation studies, though a few experiments have failed to replicate their findings. Some religious ecstatics, however, become so absorbed in trance that they inhibit or entirely suppress their responses to the outer world. Early studies by Bagchi and Wenger compared yogis and Zen masters in this regard, and appeared to show significant differences in EEG response between the two kinds of meditation. The yogis they studied habituated to repeated stimuli more rapidly and completely than Zen masters, leading Bagchi and Wenger to speculate that the two types of discipline produced different spiritual results—either inner absorption or heightened awareness of the outer world. The following studies report that meditation leads to a heightened perceptual awareness, in which the EEGs remain responsive to repeated stimuli such as clicks or light flashes instead of habituating to them: Delmonte (1984b), McEvoy et al. (1980), Davidson (1976), Williams and West (1975, Hirai (1974), Wada and Hamm (1974), Banquet (1973), Orme-Johnson (1973), Gellhorn and Kiely (1972), Naranjo and Ornstein (1971), Wallace et al. (1971b), Wallace (1971), Akishige 1970), Kasamatsu and Hirai (1963, 1966), Anand et al. (1961a), and Bagchi and Wenger (1957).
Other studies, however, failed to replicate this finding. Heide (1986) compared seventeen TM meditators and seventeen controls and found no significant differences between groups in the rate of habituation of alpha blocking. Becker and Shapiro (1981) used three groups of Zen, yoga, and TM meditators with five to seven years of experience, and two groups of controls. They found that EEG alpha suppression in response to repeated stimuli did not differ among the five groups. West (1980a) concluded that too few systematic studies of habituation have been made to reach a solid conclusion. Barwood et al. (1978) tested auditory-evoked potentials of eight experienced meditators before, during, and after meditation, and also during light sleep, and found no consistent changes between baseline and meditating or meditating and sleep auditory-evoked potentials.
Specific Cortical Control
Traditional teachers did not have electroencephalographs to study cortical activity, but the findings in modern studies that meditators achieve various kinds of control over specific kinds of brain function conform to the tenet of many contemplative literatures that self-awareness brings self-mastery. As various kinds of functioning are brought to consciousness, their integration can be more deliberately guided, according to most traditional teachings. Several modern studies seem to show that meditators do indeed acquire control of specific brain functions.
Delmonte (1984b) concluded that meditation practice may begin with left-hemisphere activity, which then gives way to functioning characteristics of the right hemisphere, while both left- and right-hemisphere activity are largely inhibited or suspended in advanced meditation.
Pagano and Frumkin (1977) reported strong evidence that meditation enhances functioning in the right hemisphere, with cumulative effects among experienced meditators. Prince (1978) suggested that meditation may inhibit the left hemisphere somewhat, shifting the focus of consciousness to the right hemisphere. Bennett and Trinder (1977) reported that TM meditators had greater flexibility in shifting from one brain hemisphere to the other. Davidson and Goleman (1977) suggested that during periods of intense concentration in meditation, sensory information may become attenuated below the level of the cortex. Earlier, Davidson (1976) reported that during mystical experience cerebral function is dominated by the right hemisphere. Goleman (1976a) stated that meditators showed a significantly increased cortical excitation during meditation and a simultaneous limbic inhibition that delinked the cortex and limbic systems. He also reported that Gurdjieff meditators' brains showed cortical specificity, or the ability to turn on those areas of the brain necessary to the task at hand while leaving the irrelevant areas inactive. Schwartz (1975) stated that meditation practices can lead to heightened cortical arousability plus decreased limbic arousability, so that perception is heightened and emotion is simultaneously reduced, which he described as a "skilled response."
Others reporting cortical specificity of response are Warrenburg (1979), Hirai (1974), Banquet (1973), and Orme-Johnson (1973).
Other Cortical Changes
Persinger (1984) stated that transient, focal, epilepticlike electrical changes in the temporal lobe, without convulsions, have been hypothesized to be primary correlates of religious experiences. He investigated two cases of this kind. The first involved the occurrence of a delta-wave dominant electrical seizure for about ten seconds, from the temporal lobe only, of a TM teacher during a peak experience. The second involved the occurrence of spikes, within the temporal lobe only, during protracted intermittent episodes of glossalalia by a member of a Pentecostal sect. Persinger concluded that religious experiences are natural correlates of temporal-lobe transients that can be detected by routine EEG measures.
Researchers have analyzed EEG differences between meditators and those in stages of sleep, hypnosis, and other self-regulation strategies. Brown et al. (1977-78) were not able to differentiate between EEG data during meditation, sleep, and therapeutic touch healing states. Fenwick et al. (1977) found that EEG results showed TM to be a method of holding the meditators' level of consciousness at stage "onset" sleep. He found no evidence to suggest that TM produced a hypometabolic state beyond that produced by muscle relaxation, nor support for the idea that TM is a fourth stage of consciousness. Pagano et al. (1976) studied the EEGs of five experienced meditators, and found appreciable amounts of sleep stages two, three, and four during meditation. Otis (1974) found during a posttreatment testing session that twenty-three Transcendental Meditators displayed significantly more sleep-stage-one activity than they had in a premeditation rest period, and significantly more sleep than controls. Rao (1965) described meditation as a form of autohypnotism parallel to the state of hypnotic trance or hypnotic sleep. On the other hand, those who have found the EEGs of meditators to be distinct include West (1979a), Wachsmuth (1978), Patey et al. (1977), Dash and Alexander (1977), Banquet and Sailhan (1974), Wallace and Benson (1972), Wallace et al. (1971b), Wallace (1971), Kasamatsu and Hirai (1966), Onda (1967), Anand et al. (1961a), and Bagchi and Wenger (1957).
A few researchers have looked at EEG results in terms of the ergotropic/trophotropic model developed by Gellhorn [see Gellhorn and Kiely (1972).] Davidson (1976) stated that mystical states may be experienced during either ergotropic (excited) or trophotropic (relaxed) conditions. He suggested that the whirling dances of Sufis and the violent abdominal contractions of Ishiguro Zen monks induce ergotropic conditions, whereas TM and other forms of sitting meditation elicit trophotropic reactions. Sargant (1974) speculated that trophotropic states may occur in the midst of an ergotropically induced experience. Gellhorn and Kiely (1972) observed that physiological changes in meditation are due to a shift in the ergotropic/trophotropic balance in the trophotropic direction—a good strategy for improving mental health. Their model was criticized by Mills and Campbell (1974), because it ignored differences in meditation techniques, left out certain evidence of alpha-blocking differences between yoga and Zen, and provided an ambiguous interpretation of trophotropic/ergotropic effects on the orienting reflex. Emerson (1972) concluded that the religion of the meditator determines the way in which his EEG pattern will change during the course of meditation. Fisher (1971) stated that the mystic may switch between extreme ergotropic and extreme trophotropic forms of mystical experience, a rebound from ecstatic rapture to yogic samadhi in response to intense ergotropic excitation. Das and Gastaut (1955) characterized the mystical state of yogic ecstacy as predominantly ergotropic, where no effect on the EEG pattern as a result of external stimuli was noticed.
Blood Chemistry
Strict comparisons between traditional understandings of bodily change in contemplative practice and modern studies of meditation's effect on blood chemistry are uncertain at best, though the finding in some studies that meditation lowers adrenal hormones, lactates, and cholesterol seems to confirm the repeated discovery that spiritual practice reduces stress and anxiety. This area of research is not as well developed, though, as other areas of meditation research. Only more investigation will reveal the intricate relationships of blood chemistry in contemplative activity.
Adrenal Hormones
Meditation generally produces psychological results opposite from those of stress, yet researchers have been puzzled by the fact that stress-induced adrenal hormone levels do not fall consistently in the blood of meditators. Benson (1983a) studied nineteen subjects who practiced the relaxation response technique twice daily for thirty days. He found increased norepinephrine levels without any increase in heart rate or blood pressure, and concluded that the relaxation response technique reduces central nervous system responsivity to norepinephrine. Or norepinephrine levels rise because less is used up by tissues that ordinarily respond to it. Benson (1989) concluded that reduced norepinephrine end-organ responsivity may be the mechanism through which physiologic changes persist after the elicitation of the relaxation response [see also Morrell (1985)]. Mills et al. (1990) measured functional lymphocyte beta-andrenergic receptors and found lower levels in TM meditators supporting Benson's hypothesis. Engle (1983), commenting on Benson's work, agreed that the relaxation response is a useful technique to modify physiological functions, but that little is understood about the mechanisms that mediate its effect. Earlier, Hoffman et al. (1982) assessed sympathetic nervous system activity in experimental subjects practicing the relaxation response and in control subjects, all of whom were exposed to graded orthostatic and isometric stress during monthly hospital visits. They found higher concentrations of norepinephrine for experimental subjects and no changes for controls [see the follow-up study by Morrell and Hollandsworth (1986) that supports this conclusion].
Sudsuang et al. (1991) reported decreased cortisol levels measured after meditation in inexperienced meditators. Michaels et al. (1979) studied eight TM meditators and eight controls, and found that cortisol decreased progressively for both groups, aldosterone did not change for either group, and renin increased by 14% for the meditation group, thereby not supporting the hypothesis that TM induces a unique state characterized by decreased sympathetic activity or release from stress. However, since cortisol concentrations varied more widely for controls than for meditators during the experiment, Michaels concluded that meditators may be less responsive to acute stress. Lang et al. (1979), in a study of ten advanced meditators with over four years of experience and ten meditators with over two years of experience, found that catecholamine levels were higher in advanced meditators during the experiment, and concluded that meditation enhances sympathetic activity. Michaels et al. (1976) measured plasma epinephrine and norepinephrine in twelve meditators before, during, and after meditation, and in a control group matched for sex and age who rested instead of meditating, and obtained the same results for both groups, thereby concluding that TM does not reduce stress and the activity of the sympathetic nervous system. Bevan et al. (1976) found significant decreases in plasma and urinary-free cortisol during TM, the effect being cumulative with increased meditation experience. However, no significant effects on catecholamine excretion were noted. He concluded that TM produces an acute and chronic reduction in trophotropic anterior hypothalamic activity but little effect on ergotropic posterior hypothalamic function, and that the mechanisms underlying the practice are not a simple counterpart of the fight-or-flight response.
Other researchers, however, have reported decreases in adrenal hormones during meditation. Werner et al. (1986) evaluated eleven subjects before and during a three-year period after starting the TM-Sidhi program. They found a progressive decrease in serum TSH, growth hormone, and prolactin levels, with no consistent change in cortisol, T4, or T3. Stone and DeLeo (1976) measured plasma dopamine-B-hydroxylase as an index of sympathetic nervous system activity in a six-month controlled trial of simple word meditation in hypertension patients. They noted significant reductions of plasma D-B-H, which was positively correlated with significant reductions of blood pressure. Schildkraut et al. (1990) found a possible common mechanism of action for the drug alprazolam (a triazolobenzodiazepine with antianxiety and antidepressant as well as antipanic effects) and elicitation of the relaxation response that involves decreased catecholamine output. Bujatti and Riederer (1976) found a significant decrease of the catecholamine metabolite VMA (vanillicmandelic acid) in meditators. This decrease was associated with a reciprocal increase of the serotonin metabolite 5-HIAA, which supports, as a feedback necessity, the rest-and-fulfillment response versus fight and flight. Loliger (1991) also reported an increase in 5-HIAA during the practice of TM and the TM-Sidhi program.
Several studies have found decreased cortisol levels in meditators versus controls with the level of effect increasing with duration of meditation practice. See Ahuja et al. (1981), Jevning et al. (1978a, 1978d), Udupa et al. (1975), and Jevning et al. (1975).
Jevning and O'Halloran (1984) stated that adrenocortical activity may be the one parameter sufficient to determine the relationship between TM and sleep, since cortisol secretion is not apparently related to sleep. They reviewed the literature, particularly Jevning, Wilson, and Davidson's study (1978), and concluded that it is unlikely that TM can be the same as sleep, or accounted for as unstylized rest/relaxation, since sharp declines of up to 25% in cortisol during meditation for long-term meditators was measured, whereas insignificant declines were noted in short-term meditators, and no changes were noted in the rest/relaxation control group.
Androgen levels are a well-established correlate of the response to acute stress, and are possibly of adrenocortical origin. Jevning and Wilson (1978) studied testosterone concentration changes during TM and during rest among a group of fifteen TM practitioners with three to five years of experience and a group of fifteen controls. The controls were restudied as practitioners after three to four months of practice. No change in testosterone concentration was found during either rest or TM. Cooper et al. (1985) studied ten experienced Transcendental Meditators and found no clear evidence that meditation suppressed stress-related hormones [see the comments of Davis (1986)].
The serum level of the adrenal androgen, dehydroepiandrosterone sulfate (DHEA-S), is closely correlated with age in humans and has also been associated with measures of health and stress. Levels of DHEA-S decrease with age, stress, and illness. Glaser et al. (1992) found generally higher levels of DHEA-S in TM meditators versus controls suggesting greater health and adaptability for meditators.
Hill (1990) studied ten meditators to investigate the acute autonomic effects of Transcendental Meditation and found that both divisions of the autonomic nervous system are attenuated. The results also provide preliminary evidence to support the hypothesis that TM is associated with acutely reduced hypothalamic and peripheral serotonergic activity.
Thyroid Hormones
Werner et al. (1986), in a study of eleven subjects in the TM-Sidhi program found decreased TSH, growth hormone, and prolactin levels and no consistent change in cortisol, T3 or T4. Jevning and Wilson (1977) found in a study of TM practitioners that T3, T4 and insulin levels did not change during meditation, but that TSH levels declined dramatically. Decreased TSH, along with stable thyroid hormone levels, may suggest change of the set point for feedback control of TSH secretion during TM and is consistent with primarily neural modulation of TSH secretion. The stability of T3, T4 and insulin make it unlikely that these hormones regulate the acute metabolic changes associated with the meditative state.
Total Protein
Sudsuang et al. (1991) reported increased serum protein levels after six weeks of meditation and speculated that cortisol reduction during meditation practice may be related to an increase in total protein because of reduction of gluconeogenesis and increased total protein synthesis by the liver.
Amino Acids and Phenylalanine
There is some evidence that amino acid metabolism is related to mental states, since alteration of plasma amino acid levels has been correlated with various forms of behavior. Jevning et al. (1977b) measured thirteen plasma neutral and acidic amino acids in twenty-eight subjects, thirteen of whom were controls and fifteen of whom had practiced TM twice daily for three to five years, and found that phenylalanine concentration increased by 23% during TM practice with no change during control relaxation. No significant changes were noted for the other twelve amino acids studied. Jevning speculated that since the liver is the principal utilizer of phenylalanine hydroxylase, reduced blood flow to the liver during meditation [see Jevning (1978c)] might be the cause of increased phenylalanine levels. He also suggested that the brain might utilize less phenylalanine during meditation.
Plasma Prolactin and Growth Hormone
Werner et al. (1986) evaluated the endocrine changes of eleven subjects before and over a three-year period after starting the TM-Sidhi program. A progressive decrease in serum thyroid stimulating hormone (TSH), growth hormone, and prolactin levels occurred over the three years, while no consistent change in cortisol, total thyroxine, or triiodothyronine was observed. Jevning, Wilson, and Vanderlaan (1978b) studied the concentrations of plasma prolactin and growth hormone before, during, and after forty minutes of TM. Twenty-four subjects were studied, including a group of twelve who had regularly practiced TM for three to five years and a group of twelve who had been regular practitioners for three to four months. The short-term practitioner group was studied as controls before, during, and after a forty-minute eyes-closed rest period. Prolactin concentration began to increase toward the end or after meditation in both groups of practitioners, with levels continuing to increase in the post-TM period. The increases were not correlated with sleep occurrence. Prolactin levels were stable in controls throughout the experiment. Growth hormone concentration was unchanged in both TM and rest groups.
Bevan et al. (1979) studied the short-term endocrine changes of five experienced meditators before, during, and after a thirty-minute period of meditation; and restudied the same group under the same experimental conditions, except that instead of meditating they read and talked quietly among themselves. A comparable group of five previously unstudied meditators were examined under the same nonmeditation conditions to offset the "second-experience" effect. A significant 38% reduction in serum hGH occurred during TM. The hGH fall commenced before the onset of meditation and appeared to be a response to anticipation of meditation. Serum hGH concentrations after TM rebounded to 50% above premeditation values. There was no change in the same subjects during a comparable nonmeditation experimental period, and the absence of hGH changes was not due to a second-experience effect. The experienced meditators showed slight decreases in prolactin and cortisol during meditation, which were not statistically significant. There were no statistically significant changes in thyroxine, triiodothyronine, reverse triiodothyronine, hemoglobi, packed cell volume, or total serum protein during the experimental period.
Lactate
High blood lactate concentrations have been associated with anxiety and high blood pressure, and the infusion of lactate in the blood has been found to produce symptoms of anxiety. The following studies have reported significant declines of up to 33% in blood lactate during meditation, and a rate of decline nearly four times faster than the rate of decrease among people resting or in a premeditation period: Bagga et al. (1981), Jevning et al. (1978c), Jevning and Wilson (1977), Benson (1975), Benson et al. (1973a, 1973b), Orme-Johnson (1973), Wallace and Benson (1972), Wallace et al. (1971a), and Wallace (1971).
Other studies have not confirmed a drop in lactate concentrations during meditation. Michaels et al. (1979) studied the plasma concentration of lactates of eight TM meditators before, during, and after twenty to thirty minutes of meditation, and of eight controls who rested quietly. Their failure to observe a change in lactate was consistent with their previously published report (Michaels et al.,1976).
White Blood Cells
Parulkar et al. (1974) studied twelve TM practitioners and found the following average decreases: white blood cell count before TM, 7,100, after TM, 6,813; eosinophil count before TM, 638, after TM, 460; and lymphocyte count before TM, 2,855, after TM, 2,781.
Red Blood Cell Metabolism
Jevning et al. (1983) studied thirty-two TM instructors with at least six years of meditation experience. They found a marked decline of whole blood metabolism during TM, which was accounted for mostly by a decline of red cell glycolite rate. This was correlated with decreased plasma lactate concentration and with relaxation as indicated by electrodermal response.
Cholesterol
Chronic sympathetic nervous system overactivity has been implicated as a factor capable of elevating and maintaining high serum cholesterol levels independent of dietary measures. Bagga et al. (1981) studied forty female medical students who practiced TM and yoga, and reported that their average serum cholesterol decreased from 196.3 mg/dl to 164.7 mg/dl. Cooper and Aygen (1979) measured serum cholesterol levels at the beginning and end of an eleven-month period for twelve hypercholesterolemic subjects who practiced TM. Eleven hypercholesterolemic controls who did not practice the technique were similarly followed for thirteen months. Paired comparisons showed a significant reduction in fasting serum cholesterol levels for those subjects who practiced meditation. The cholesterol mg per 100 ml for the meditation group was 254 at the start and 225 at the end of the period, and for the control group it was 259 at the start and 254 at the end of the period.