Norepinephrine alterations under stress conditions following the regular practice of meditation

The present study reexamined an investigation that found enhanced plasma norepinephrine (NE) levels during isometric handgrip after 30 days of meditation practice. Since hemodynamic activity did not show corresponding increases, it was suggested that meditation had down regulated the cardiovascular response to sympathetic stimulation. The present study assessed response to venipuncture as well as isometric stress. At posttest, meditators showed a trend towards higher plasma NE levels than controls during isometric handgrip. However, in contrast to previous speculation, this did not appear to represent cardiovascular down-regulation. At the same time, meditators produced the greater NE levels during venipuncture, accompanied by marginally lower heart rate. The results support the association between regular meditation and noradrenergic hyperactivation, but suggest the need for further investigation of underlying mechanisms.     

Hormonal control in a state of decreased activation: potentiation of arginine vasopressin secretion

Behaviorally induced stress is associated with increased arginine vasopressin (AVP) secretion. In this report we describe a phasic conditioned response of AVP secretion yielding 2.6-7.1 times normal plasma concentration of this hormone in association with a physiological state of decreased activation, that associated with the mental technique of "transcendental meditation" (TM) in long-term practitioners (6-8 years of regular elicitation). Such a very large phasic response of AVP was previously unknown in the normal physiology of AVP. This elevation was not accompanied by elevation of plasma osmolality. Unstylized ordinary eyes closed rest in a separate group of subjects studied in the same manner was associated with normal plasma AVP concentration. Galvanic skin resistance (GSR) increased during both TM and rest with significantly larger increase associated with TM. Other measures of activation, including muscle metabolism, and the Spielberger Anxiety Inventory indicated marked relaxation in association with TM. In previous research it has been shown that blood pressure does not change acutely during this behavior. These observations indicate that neither stress nor operation of other usual homeostatic control mechanisms are responsible for elevated for AVP in the meditators. It is speculated that the apparently unique mechanism of TM-induced AVP secretion may be more specifically related to the behavioral effects of meditation.     

Psychophysiological Responsiveness to Auditory Stimulation during Transcendental Meditation

The Transcendental Meditation (TM) technique has been reported to produce cortical states of both steady responsiveness and lack of responsiveness to external stimulation during meditation. The present study examined alpha blocking, skin conductance, and phasic heart rate response to 80dB tones in 17 TM meditators and 17 controls. There were no significant differences between groups in rate of habituation of alpha blocking or skin conductance response, and neither group showed habituation of heart rate responding. Controls displayed a more labile and accelerative cardiac response. Results suggest the possible usefulness of cardiac waveform activity in the study of meditation.     

Physiological Responses to Clicks during Zen, Yoga, and TM Meditation

Two studies have been widely quoted as indicating the differing states of consciousness in Zen vs Yoga meditation. A replication and extension were attempted. Very experienced Zen, Yoga, and TM meditators with average lengths of experience of 7.5 yrs, 5 yrs, and 7 yrs, respectively, and two groups of controls were presented with auditory clicks during meditation. EEG alpha suppression and skin conductance response both showed clear habituation which did not differ among groups, thus failing to replicate the earlier studies. The N100, P200, and P300 components of the EEG average evoked potential were also measured.     

Meditation potentially capable of increasing susceptibility to epilepsy - a follow-up hypothesis

In an earlier article entitled "Meditation may predispose to epilepsy: an insight into the alteration in brain environment induced by meditation" published in Medical Hypotheses 2005:64(3):464-7, the author has hypothesized that meditation exerts predisposing influence on epileptogenesis. The hypothesis is based on certain EEG changes and electrographic features (namely hypersynchrony and coherence of EEG activity) and increase in chemical transmitters (namely glutamate and serotonin) in the brain during the course and attainment of meditation. This paper aims to further strengthen the hypothesized predisposing influence of meditation on epilepsy by providing stronger evidences and with more elaboration. Studies on meditators have reported various adverse outcomes and one such study has indeed revealed significantly higher incidence of complex partial epileptic-like signs and experiences in a large number (n = 221) of meditators compared to non-meditators (controls n = 860), the researcher claiming "cognitive kindling" by meditation to be the underlying basis. These studies thus do highlight and underscore the strong influence of meditation in increasing susceptibility to epilepsy.     

Physiological Changes in Yoga Meditation

A group of 11 meditators using Ananda Marga Yoga techniques were matched individually with non-meditating controls. Controls were instructed to remain “wakefully relaxed” for 40 min, while the others meditated for the same amount of time. Six of the 11 controls fell asleep during the 40 min (defined by K-complexes and spindles in the EEG), while none of the meditators fell asleep. Rather, meditators remained in a relatively stable state of alpha and theta EEG activity. Meditation was also characterized by a marked increase in basal skin resistance and by a decrease in respiratory rate, changes which were not observed in the controls. Some physiological changes observed during meditation continued into the post-meditation resting periods. These findings suggest that Ananda Marga meditation produces a physiological effect different from that observed in controls who try to relax with their eyes closed.     

The effects of running and meditation on beta-endorphin, corticotropin-releasing hormone and cortisol in plasma, and on mood

The relations between three hormones of the hypothalamic-pituitary-adrenocortical (HPA) axis, beta-endorphin (β-EP), corticotropin-releasing hormone (CRH) and cortisol, and mood change were examined in 11 elite runners and 12 highly trained meditators matched in age, sex, and personality. Despite metabolic differences between running and meditation, we predicted that mood change after these activities would be similar when associated with similar hormonal change. Compared to pre-test and control values, mood was elevated after both activities but not significantly different between the two groups at post-test. There were significant elevations of β-EP and CRH after running and of CRH after meditation, but no significant differences in CRH increases between groups. CRH was correlated with positive mood changes after running and meditation. Cortisol levels were generally high but erratic in both groups. We conclude that positive affect is associated with plasma CRH immunoreactivity which itself is significantly associated with circulating β-EP supporting a role for CRH in the release of β-EP. Increased CRH immunoreactivity following meditation indicates, however, that physical exercise is not an essential requirement for CRH release.     

Differential engagement of anterior cingulate and adjacent medial frontal cortex in adept meditators and non-meditators

This study investigated differences in brain activation during meditation between meditators and non-meditators. Fifteen Vipassana meditators (mean practice: 7.9 years, 2h daily) and fifteen non-meditators, matched for sex, age, education, and handedness, participated in a block-design fMRI study that included mindfulness of breathing and mental arithmetic conditions. For the meditation condition (contrasted to arithmetic), meditators showed stronger activations in the rostral anterior cingulate cortex and the dorsal medial prefrontal cortex bilaterally, compared to controls. Greater rostral anterior cingulate cortex activation in meditators may reflect stronger processing of distracting events. The increased activation in the medial prefrontal cortex may reflect that meditators are stronger engaged in emotional processing.     

不同部位麻醉手术对肾素,血管紧张素,醛固酮和皮质醇的影响

应用放免分析法，分别对胸段连续硬膜外麻醉于行上腹部手术（Ａ组，１２例）和腰段连续硬膜外麻醉下行盆腔或下肢手术（Ｂ组，１２例）围手术期血浆肾素活性（ＰＲＡ），血管紧张素Ⅱ（ＡⅡ）醛固酮（ＡＬＤ）和皮质醇（ＣＯＲ）监测，其结果显示：Ａ组ＰＲＡ，ＡＬＤ和ＣＯＲ变化有显著意义（Ｐ〈０．０５），而Ｂ组的变化无显著意义（Ｐ〉０．０５）；同时通过对两组转术期血流动力学观察，显示Ａ组血压和心率降低幅度小于Ｂ组，表     

Impact of long-term meditation practice on cardiovascular reactivity during perception and reappraisal of affective images

Meditation has been found to be an efficient strategy for coping with stress in healthy individuals and in patients with psychosomatic disorders. The main objective of the present study was to investigate the psychophysiological mechanisms of beneficial effects of meditation on cardiovascular reactivity. We examined effects of long-term Sahaja Yoga meditation on cardiovascular reactivity during affective image processing under “unregulated” and “emotion regulation” conditions. Twenty two experienced meditators and 20 control subjects participated in the study. Under “unregulated” conditions participants were shown neutral and affective images and were asked to attend to them. Under “emotion regulation” conditions they down-regulated negative affect through reappraisal of negative images or up-regulated positive affect through reappraisal of positive images. Under “unregulated” conditions while anticipating upcoming images meditators vs. controls did not show larger pre-stimulus total peripheral resistance and greater cardiac output for negative images in comparison with neutral and positive ones. Control subjects showed TPR decrease for negative images only when they consciously intended to reappraise them (i.e. in the “emotion regulation” condition). Both meditators and controls showed comparable cardiovascular reactivity during perception of positive stimuli, whereas up-regulating of positive affect was associated with more pronounced cardiac activation in meditators. The findings provide some insight into understanding the beneficial influence of meditation on top-down control of emotion and cardiovascular reactivity.     

Increased default mode network connectivity associated with meditation

Areas associated with the default mode network (DMN) are substantially similar to those associated with meditation practice. However, no studies on DMN connectivity during resting states have been conducted on meditation practitioners. It was hypothesized that meditators would show heightened functional connectivity in areas of cortical midline activity. Thirty-five meditation practitioners and 33 healthy controls without meditation experience were included in this study. All subjects received 4.68-min resting state functional scanning runs. The posterior cingulate cortex and medial prefrontal cortex were chosen as seed regions for the DMN map. Meditation practitioners demonstrated greater functional connectivity within the DMN in the medial prefrontal cortex area (xyz=339-21) than did controls. These results suggest that the long-term practice of meditation may be associated with functional changes in regions related to internalized attention even when meditation is not being practiced.     

Modulation of red cell metabolism by states of decreased activation: comparison between states

Marked decline of red cell metabolism has been described during the acute state of decreased activation associated with the stylized mental technique of transcendental meditation (TM) in long-term meditators (5-10 years regular elicitation, TM instructors). It is not known whether unstylized rest is accompanied by a similar effect and it is not known what effector(s) may contribute to red cell metabolic changes in these states. In the present study ordinary, unstylized rest was found to be accompanied by small increase of red cell glycolytic rate. Apparently, either repeated elicitation of TM behavior or some special feature of this practice become associated with new mechanisms of metabolic control than those previously in operation. Although the data of this study do not permit isolation of the precise psychological determinants of this effect, the range of possible physiological effectors can be delimited. Blood pH, PCO2, PO2, and phosphate can be eliminated as significant for red cell metabolic control during both TM and rest, and based upon related studies, several known hormones such as insulin, T3, T4, arginine vasopressin, oxytocin, prolactin and growth hormone can also be eliminated as responsible effector(s).     

Effects of meditation practice on spontaneous eyeblink rate

A rapidly growing body of research suggests that meditation can change brain and cognitive functioning. Yet little is known about the neurochemical mechanisms underlying meditation‐related changes in cognition. Here, we investigated the effects of meditation on spontaneous eyeblink rates (sEBR), a noninvasive peripheral correlate of striatal dopamine activity. Previous studies have shown a relationship between sEBR and cognitive functions such as mind wandering, cognitive flexibility, and attention–functions that are also affected by meditation. We therefore expected that long‐term meditation practice would alter eyeblink activity. To test this, we recorded baseline sEBR and intereyeblink intervals (IEBI) in long‐term meditators (LTM) and meditation‐naive participants (MNP). We found that LTM not only blinked less frequently, but also showed a different eyeblink pattern than MNP. This pattern had good to high degree of consistency over three time points. Moreover, we examined the effects of an 8‐week course of mindfulness‐based stress reduction on sEBR and IEBI, compared to an active control group and a waitlist control group. No effect of short‐term meditation practice was found. Finally, we investigated whether different types of meditation differentially alter eyeblink activity by measuring sEBR and IEBI after a full day of two kinds of meditation practices in the LTM. No effect of meditation type was found. Taken together, these findings may suggest either that individual difference in dopaminergic neurotransmission is a self‐selection factor for meditation practice, or that long‐term, but not short‐term meditation practice induces stable changes in baseline striatal dopaminergic functioning.     

Acute increases in night-time plasma melatonin levels following a period of meditation

To determine whether a period of meditation could influence melatonin levels, two groups of meditators were tested in a repeated measures design for changes in plasma melatonin levels at midnight. Experienced meditators practising either TM-Sidhi or another internationally well known form of yoga showed significantly higher plasma melatonin levels in the period immediately following meditation compared with the same period at the same time on a control night. It is concluded that meditation, at least in the two forms studied here, can affect plasma melatonin levels. It remains to be determined whether this is achieved through decreased hepatic metabolism of the hormone or via a direct effect on pineal physiology. Either way, facilitation of higher physiological melatonin levels at appropriate times of day might be one avenue through which the claimed health promoting effects of meditation occur.     

Renin, aldosterone and cortisol during ethanol intoxication and hangover.

The effect of ethanol intoxication and hangover on plasma renin activity (PRA), plasma aldosterone (PA) and plasma cortisol (PC) concentrations was studied in 7 healthy supine men in controlled clinical conditions during 18 h beginning at 6 p.m. Large individual variation was observed in the response of PRA, PA and PC to ethanol. Following ethanol, stimulation of PRA was observed at the 14th and the 16th hour (P less than 0.05), of PA at the 4th and the 6th hour (P less than 0.01 and P less than 0.05, respectively) and of PC at the 4th and the 14th hour (P less than 0.01 and P less than 0.05, respectively). Ethanol ingestion suppressed PC during the first hour (P less than 0.02). Water ingestion at 8 a.m. suppressed PA between the 14th and the 16th hour (8-10 a.m.) in control and ethanol experiment (P less than 0.01 and P less than 0.005, respectively). There was a dissociation between PRA and PA, but intra-individually PRA and PA correlated fairly or well. Plasma arginine vasopressin (AVP) and PC were also significantly correlated. The results suggest that changes in PA and PC as well as the dissociation of PRA and PA after ethanol ingestion might be partly related to dehydration and to the increased secretion of hypothalamic and pituitary hormones as well as to sodium and potassium balance. There was a biphasic effect of ethanol, including an inital suppression of PC and a subsequent increase of PC, PRA and PA. Upright posture appears to exaggerate the stimulating effect of ethanol on PRA, PA and PC.     

Meditators and Non-Meditators: EEG Source Imaging During Resting

Many meditation exercises aim at increased awareness of ongoing experiences through sustained attention and at detachment, i.e., non-engaging observation of these ongoing experiences by the intent not to analyze, judge or expect anything. Long-term meditation practice is believed to generalize the ability of increased awareness and greater detachment into everyday life. We hypothesized that neuroplasticity effects of meditation (correlates of increased awareness and detachment) would be detectable in a no-task resting state. EEG recorded during resting was compared between Qigong meditators and controls. Using LORETA (low resolution electromagnetic tomography) to compute the intracerebral source locations, differences in brain activations between groups were found in the inhibitory delta EEG frequency band. In the meditators, appraisal systems were inhibited, while brain areas involved in the detection and integration of internal and external sensory information showed increased activation. This suggests that neuroplasticity effects of long-term meditation practice, subjectively described as increased awareness and greater detachment, are carried over into non-meditating states.     

Abnormal response to metabolic stress in schizophrenia: marker of vulnerability or acquired sensitization?

BACKGROUND: Previous work suggests that individuals with schizophrenia display an altered homovanillic acid (HVA) response to metabolic stress. The present study replicated and extended this paradigm, including individuals with elevated genetic risk for schizophrenia. METHOD: Patients with psychosis (n = 50), non-psychotic first-degree relatives of patients with psychosis (n = 51) and controls without psychosis (n = 50) underwent, in randomized order, double-blind administration of placebo and the glucose analogue 2-deoxy-D-glucose (2DG), which induces a mild, transient clinical state of glucoprivation. Plasma HVA and cortisol were assessed twice before the start of the 2DG/placebo infusion (baseline values), as well as four times post infusion. Data were analysed using multi-level random regression techniques. RESULTS: During the stress condition, significant increases in plasma HVA and cortisol were found. The increase in plasma HVA level during the stress condition was significantly stronger in patients than in controls, whereas this was not the case in relatives v. controls. The increase in plasma cortisol during the stress condition was significantly less in patients than controls, but no significant difference in the increase of plasma cortisol during stress was found in the comparison between relatives and controls. CONCLUSIONS: Patients with psychosis, but not their non-psychotic first-degree relatives, show an altered neurobiological response to metabolic stress, suggesting that this dysregulation is not a genetically transmitted vulnerability, but an illness-related effect, possibly reflecting acquired sensitization of neuroendocrine systems by repeated environmental stressors or repeated stimulation with agonistic drugs.     

The effect of sodium load on the development of hypertension, plasma renin and kininogen in rats with renal artery constriction

Effects of sodium load on the development of hypertension, plasma renin activity (PRA) and kininogen were studied in rats with renal artery constriction and untouched contralateral kidney. After the operation or sham-operation, 0.9% NaCl or water were given as drinking fluid. A marked hypertension (systolic pressure greater than 150 mmHg) developed in all operated rats on saline, but only in 2/3 of operated rats on water. In none of the sham-operated controls did systolic pressure exceed 150 mmHg during 7 postoperative weeks. Within the operated group on water, hypertensive rats had significantly higher PRA values than normotensive animals (P less than 0.05). Salt load slightly suppressed the PRA in sham-operated rats but not in animals with constriction renal artery, compared to sham-operated controls on water. The operated rats on salt excess had higher plasma kininogen levels than the operated normotensive rats on water (P less than 0.05), but there were no other significant differences in kininogen values between different study groups, regardless of whether blood pressure was increased or not. The results indicate that in this form of hypertension, the high blood pressure can be maintained without any increase in PRA if animals are subjected to a sodium load which sensitizes vascular beds to angiotensin. The increase in plasma kininogen, suggesting suppression of kallikrein-kinin system, is unlikely associated with the increase of blood pressure.     

Serial measurements of plasma renin activity, aldosterone and cortisol during percutaneous transluminal angioplasty of the renal artery in man

Fifteen patients (eight men, seven women) with hypertension and renal artery stenosis underwent dilation of the stenosis by percutaneous transluminal renal angioplasty (PTRA). During and shortly after this treatment the effects on the renin-angiotensin-aldosterone system and blood pressure were studied. Plasma renin activity (PRA) was measured in peripheral blood and in renal venous blood during the PTRA. PRA increased in peripheral blood during PTRA as a result of an immediate significant rise in renal venous plasma renin activity by 132 +/- 134% (P less than 0.01) on the dilated side. PRA in the contralateral renal vein was close to that in peripheral blood. Within 10 min after PTRA there was a significant increase in serum aldosterone from 439 +/- 343 to 774 +/- 635 pmol 1-1 (P less than 0.025), while serum cortisol remained unchanged. The aldosterone increase was most probably mediated by angiotensin II. Systolic and diastolic blood pressures were unchanged during PTRA in spite of renin and aldosterone increases, suggesting that antihypertensive factors counteract the pressor effects of a physiologically relevant increase in PRA.     

Zen meditation and ABC relaxation theory: an exploration of relaxation states, beliefs, dispositions, and motivations

This study is an attempt to rigorously map the psychological effects of Zen meditation among experienced practitioners. Fifty-nine Zen meditators with at least six years of experience practiced an hour of traditional Zazen seated meditation. A control group of 24 college students spent 60 min silently reading popular magazines. Before relaxation, all participants took the Smith Relaxation States Inventory (SRSI), the Smith Relaxation Dispositions/Motivations Inventory (SRD/MI), and the Smith Relaxation Beliefs Inventory (SRBI). After practice, participants again took the SRSI. Analyses revealed that meditators are less likely to believe in God, more likely to believe in Inner Wisdom, and more likely to display the relaxation dispositions Mental Quiet, Mental Relaxation, and Timeless/Boundless/Infinite. Pre- and postsession analyses revealed that meditators showed greater increments in the relaxation states Mental Quiet, Love and Thankfulness, and Prayerfulness, as well as reduced Worry. Results support Smith's ABC Relaxation Theory.