- увеличивает концентрацию дофамина в лимбической системе на две трети (нейротрасмитер, отвечающий за мотивацию и абстрактное очущение радости);
- увеличивает концентрацию в плазме серотонина и мелатонина (оба гормона тесно связаны и отвечают за стабилизацию настроения, поддержку иммунитета, задержку старения, общее ощущение благосостояния);
- улучшает способность к восприятию новой информации, внимание, сосредоточенность и время реакции;
- значительно снижает подверженность личностным расстройствам, включая нарциссизм и тревожность, склоннось к неврозам, психозам и депрессии;
- увеличивает толщину коры в правой средней и верхней лобной доле и островке. Обычная атрофия этих областей коры, связанная с возрастом и потерей нейронов, у медитаторов значительно задерживается или отсутствует. Так, толщина коры этих областей мозга у 50-летних медитаторов была сравнима с таковой у 20-30 летних в контрольной группе;
- у медитаторов увеличена концентрация нейронов в правом островке и гиппокампе, а также в левой нижней височной доле (области отвечающие за долгосрочную память и внимание). Это увеличение коррелирует с количеством часов, проведенных в медитации на протяжении жизни (т.е. количество нейронов можно также "накачивать", как и мышцы в спортзале, это к старому мифу о том, что нервные клетки не восстанавливаются).
Further evidence supporting the hypothesis that Meditation experiences are related to limbic brain activation comes from studies that show Meditation-elicited changes in neurochemicals that are released by limbic brain regions and modulate mood and affect. A functional imaging study using PET compared rest (listening to speech) to active Meditation (Meditation under verbal instruction) during Yoga Nidra Meditation. This relaxation Meditation method is based on breathing exercises that induce a detached state characterised by reduced readiness for action and enhanced sensory awareness (Kjaer et al., 2002).
They found decreased binding of a radioactive tracer that competes with endogenous dopamine in the ventral striatum. This corresponds to about 65% increase in dopamine release in limbic brain regions. Dopamine is a neurotransmitter that is crucial for motivational and fronto-limbic affective systems of the brain. The increase in dopamine was correlated with increase in theta activity, thought to reflect enhanced internalised attention (Kjaer et al., 2002). The findings of dopamine release in limbic brain regions is also in line with the above reported activation findings in left frontal and limbic areas during the abstract sense of joy using the same Meditation technique (Lou et al., 1999).
Several studies of Meditation have observed increases in blood plasma levels of melatonin ([Harinath et al., 2004], [Massion et al., 1995], [Solberg et al., 2000a], [Solberg et al., 2004a], [Solberg et al., 2004b] and [Tooley et al., 2000]) and serotonin ([Bujatti and Riederer, 1976], [Solberg et al., 2000a], [Solberg et al., 2004b] and [Walton et al., 1985]), chronically in long-term Meditators compared to controls or acutely after Meditation.
Both neurochemicals are closely linked, play an important role in mood stabilisation, positive affect, stress-prevention and aging and there is evidence for their implications in affective disorders such as depression ([Young and Leyton, 2002], [Neumeister, 2003], [Stockmeier, 2003] and [Pacchierotti et al., 2001]). Melatonin has been shown to have a stimulating effect on the immune system and the antioxydative defense system, thus delaying aging ([Brzezinski, 1997] and [Massion et al., 1995]); a meta-analysis on 10 randomised controlled trials of melatonin in tumor patients showed that melatonin significantly reduced the risk of death at 1 year follow-up (Mills et al., 2005). It is thus very likely that the subjective feelings of general well-being and positive affect during Meditation are at least in part mediated by the release of mood stabilising neuro-hormones and neurotransmitters (dopamine, serotonin, and melatonin) in limbic brain regions.
Evidence exists for long-term improvements with Meditation in cognitive skills, mainly in the domains of attention, inhibitory control and perceptual sensitivity. Thus, long-term Meditators have been shown to be superior to controls in selective and sustained attention and inhibitory control as well as in EEG neurophysiological correlates of performance (Cahn and Polich, 2006).
Furthermore, several studies have shown enhanced perceptual acuity and enhanced attentional and inhibitory skills in long-term practitioners of Mindfulness Meditation practice ([Brown et al., 1984], [Jha et al., 2007] and [Slagter et al., 2007]) and one-pointedness Tibetan Buddhist Meditation (Carter et al., 2005). Improvements in reaction time and executive functions have also been reported in practitioners of other Buddhist Meditation techniques (Sudsuang et al., 1991).
These benefits in tasks of inhibitory self-control, attention and perception are likely to reflect the long-term effects of concentrative practices that teach attentional focus and the inhibition of task-irrelevant external and internal activity such as thoughts or environmental distraction. Remarkably, there is evidence that even very short-term Meditation based mental training of weeks to months can enhance performance on attention tasks ([Slagter et al., 2007] and [Tang et al., 2007]).
A study of Aftanas and Golosheykin (2005) compared 27 long-term Meditators of Sahaja Yoga to controls on a range of trait personality measures. The long-term Meditators scored significantly lower in personality features of anxiety, neuroticism, psychoticism, and depression and scored higher in emotion recognition and expression (Aftanas and Golosheykin, 2005). The authors suggested that long-term Meditation leads to higher psycho-emotional stability and better emotional skills.
Only two studies, to our knowledge, have examined the long-term plastic effects of Meditation on brain structure. Lazar et al. (2005) compared 20 Buddhist Meditators who practised insight/Mindfulness Meditation for an average time of 9 years to age and demographically matched controls. The authors searched for changes between groups in apriori defined regions of the frontal lobe, interoceptive and unimodal sensory regions. The Meditators compared to controls had significantly increased cortical thickness in right middle and superior frontal cortex and the insula. Furthermore, these areas were significantly negatively correlated with age in controls but not Meditators, suggesting that in the Meditators the normal age-related cortical thinning is delayed in right fronto-limbic brain regions (Lazar et al., 2005). The thickness of the right prefrontal regions in 40–50-year-old Meditators was comparable to the thickness in 20–30-year-old controls and young Meditators.
The second study also investigated structural differences in 20 practitioners of 2–16 years of Vipassana Mindfulness Meditators compared to age and demographically well-matched controls. The Meditators had increased grey matter concentration in right insula and hippocampus and at a trend level in left inferior temporal lobe. Left inferior temporal lobe and at a trend level the insula grey matter concentration increases correlated significantly with the lifetime hours of Meditation practice (Hoelzel et al., 2007).
The right prefrontal cortex is known to be crucial for sustained attention and concentration functions, and the increased thickness probably reflects Meditation-induced cortical plasticity due to years of dedicated concentration practice. The insula, found to be increased in both studies, is an area that is important for interoceptive attention and breath awareness (Critchley et al., 2004). An experience-dependent plastic change in this region may reflect the specific Meditation practice of focussing attention to internal and visceral functions, thus enhancing body awareness. The hippocampus plays an important role in cortical arousal and via its connections to the amygdala influences emotional and attentional processes ([de Curtis and Pare, 2004] and [Wu and Guo, 1999]). Interestingly, across the whole brain, gray matter concentration in the medial orbitofrontal region, an area known to be important for emotion control, correlated with the years of Meditation practiceю
There is also evidence that Meditation induces lasting changes in brain function. EEG studies show that the typical slow-wave (alpha-theta) brain patterns elicited during concentration Meditation techniques of different Yoga traditions are also observed during rest, thus showing lasting trait effects ([Aftanas and Golosheykin, 2005] and [Cahn and Polich, 2006]). This may suggest that long-term Meditators when resting enter into a semi-meditative state or achieve a permanent reduction of the internal mental dialogue. Sahaja Yoga Meditators during rest have also shown a reduction of the typical left over right hemispheric asymmetry observed in parietal lobes of healthy controls, suggesting enhanced hemispheric balance (Aftanas and Golosheykin, 2005). Transcendental Meditation, a commercial Meditation technique with relatively secretive, non-concentrative practices involving mantra repetition, has also shown to elicit long-term functional brain changes. Long-term transcendental Meditation practitioners showed thus cumulative effects of the frequency of transcendent experiences on cortical preparatory response in ERP measures, concomitant with enhanced selective attention ([Travis et al., 2000] and [Travis et al., 2002]).
An interesting study investigating the neural correlates of emotional reactivity of long-term Meditators compared to controls showed reduced psychological, physiological and electrophysiological reactivity to stressful stimuli, providing for the first time neurophysiological evidence to support the hypothesis that Meditation leads to "detachment" and greater emotional resilience to stressful life events (Aftanas and Golosheykin, 2005). Twenty-five Sahaja Yoga Meditators were compared to controls in their response to a stressful video-clip. The Meditators compared to controls showed reduced subjective ratings of negative emotions elicited by the movie, reduced levels of an autonomic indicator of stress (skin potential levels) and reduced gamma activity over frontal brain regions in response to the stressful stimuli. Gamma activity over frontal regions in the control group is reflective of increased focused arousal in relation to the emotional involvement and reactivity ([Jausovec and Jausovec, 2005] and [Rennie et al., 2000]). These findings provide neurophysiological evidence for the claim for long-term effects of Meditation on emotional stability, detachment and resilience to stressful events.
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