Brain activity and meditation

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Highlighted region shows the anterior cingulate cortex, a region of the brain shown to be activated during meditation. MRI anterior cingulate.png
Highlighted region shows the anterior cingulate cortex, a region of the brain shown to be activated during meditation.

Meditation and its effect on brain activity and the central nervous system became a focus of collaborative research in neuroscience, psychology and neurobiology during the latter half of the 20th century. Research on meditation sought to define and characterize various practices. The effects of meditation on the brain can be broken up into two categories: state changes and trait changes, respectively alterations in brain activities during the act of meditating and changes that are the outcome of long-term practice.

Contents

Mindfulness meditation, a Buddhist meditation approach found in Zen and Vipassana, is frequently studied. [1] [2] Jon Kabat-Zinn describes mindfulness meditation as complete, unbiased attention to the current moment. [3]

Changes in brain state

Electroencephalography

Electroencephalography (EEG) has been used in many studies as a primary method for evaluating the meditating brain. Electroencephalography uses electrical leads placed all over the scalp to measure the collective electrical activity of the cerebral cortex. Specifically, EEG measures the electric fields of large groups of neurons. EEG has the benefit of excellent temporal resolution and is able to measure aggregate activity of portions or the entire cortex down to the millisecond scale. Unlike other imaging based methods, EEG does not have good spatial resolution and is more appropriately used to evaluate the running spontaneous activity of the cortex. This spontaneous activity is classified into four main classifications based on the frequency of the activity, ranging from low frequency delta waves (< 4 Hz) commonly found during sleep to beta waves (13–30 Hz) associated with an awake and alert brain. In between these two extremes are theta waves (4–8 Hz) and alpha waves (8–12 Hz). [4]

Many studies on mindfulness meditation, assessed in a review by Cahn and Polich in 2006, have linked lower frequency alpha waves, as well as theta waves, to meditation. [5] Much older studies report more specific findings, such as decreased alpha blocking and increased frontal lobe specific theta activity. [6] Alpha blocking is a phenomenon where the active brain, normally presenting beta wave activity, cannot as easily switch to alpha wave activity often involved in memory recall. These findings would suggest that in a meditative state a person is more relaxed but maintains a sharp awareness. Two large, comprehensive review works, however, point to poor control and statistical analyses in these early studies and comment that it can only be said with confidence that increased alpha and theta wave activity exists. [5] [7]

A statue of Amitabha meditating. Kamakura Budda Daibutsu front 1885.jpg
A statue of Amitābha meditating.

Neuroimaging

Functional magnetic resonance imaging (fMRI) is another highly utilized methodology for studying state changes in meditating brains. fMRI detects subtle increases in blood flow to areas of the brain with higher metabolic activity. Thus these areas of increased metabolic activity indicate which regions of the brain are currently being used to process whatever stimuli presented. Counter to EEG, the advantage of fMRI is its spatial resolution, with the ability to produce detailed spatial maps of brain activity. It suffers, however, in temporal resolution and cannot measure progressive activity, like the EEG, with much detail.

Topographical findings

As a relatively new technology, fMRI has only recently been used to assess brain state changes during meditation. Studies have shown heightened activity in the anterior cingulate cortex, frontal cortex, and prefrontal cortex, specifically in the dorsal medial prefrontal area during Vipassana meditation. [8] Similarly, the cingulate cortex and frontal cortex areas were shown to have increased activity during Zen meditation. [9] Both studies comment on the possibility that these findings could indicate some state of heightened voluntary control over attention during mindfulness meditation. Review works by Cahn and Chiesa state that these results indicate consistency in meditation's effect on these regions of the brain, citing a multitude of other studies spanning other meditative disciplines, but mention the need for further investigation with better controls. [5] [7]

Study on meditation and emotion

The review by Cahn also notes findings describing a heightened emotional state of meditators. A more complex study, conducted in 2008 by Lutz et al., focused on emotional response during meditation. [10] This investigation involved the creation of a "compassion meditation" state by novice and experienced meditators and testing the meditators response to emotionally charged sounds. fMRI results indicated heightened activity in the cingulate cortex but also in the amygdala, temporo-parietal junction, and right posterior superior temporal sulcus in response to the emotional sounds. The authors of this study believe this indicates greater sensitivity to emotional expression and positive emotion due to the neural circuitry activated. [10]

Changes in brain due to the prolonged practice

Electroencephalography

Similar to research into state changes in brain function, older studies make more specific claims about trait changes in meditators versus non-meditators. Changes to the alpha wave were indicated to be a trait, as well as state and phenomena. Studies have reported an increase in the specific frequencies expressed in the alpha range, increased alpha band power, and an overall slowing (reduction in frequency) in EEG activity in experienced meditators versus less experienced meditators while meditating. [6] [11] The alpha blocking phenomena, observed as a state change in brain function, was investigated as a possible trait change as well. One study that examined a variety of meditation techniques tried to show that alpha blocking was affected by the long term practice of meditation by testing response to auditory stimuli. [12] Review works, however, comment on inconsistent findings as well as a lack of repeated results in this, and other studies. They further remark that, similar to observations in brain state changes, only general assertions can be made about brain trait changes: some change in the electroencephalographic profile exists but with some inconsistency. [5] [13] It is also important to note that these trait changes were observed during meditation, and although it does indicate that a practitioner's electroencephalographic profile is modified by the practice of meditation, these EEG studies have not yet shown changes in non-meditating brains, even of experienced meditators.

Red region of the brain shows the hippocampus which had been shown to have heightened activity during meditation by experienced meditators. Hippocampus.gif
Red region of the brain shows the hippocampus which had been shown to have heightened activity during meditation by experienced meditators.

Neuroimaging

Brain trait changes have also been observed in neuroimaging studies, most often employing fMRI. In a meta-analysis of 21 neuroimaging studies, eight brain regions were found to be consistently altered, including areas key to meta-awareness (frontopolar cortex/Brodmann area 10), exteroceptive and interoceptive body awareness (sensory cortex and insular cortex), memory consolidation and reconsolidation (hippocampus), self and emotion regulation (anterior cingulate cortex and orbitofrontal cortex), and intra- and interhemispheric communication (superior longitudinal fasciculus; corpus callosum) [14] These changes were distinguished by density increases in grey matter regions and white matter pathways in the brains of individuals who meditate in comparison to individuals who do not. Of all areas with reported findings, a greater number of structural changes were found in the left hemisphere.

There is also evidence to suggest meditation plays a protective role against the natural reduction in grey matter volume associated with aging. One study found evidence that Zen meditators experienced a slower age related decline rate for cerebral gray matter volume in the putamen which plays a role in learning, cognitive flexibility and attentional processing [15] This could suggest a better attentiveness in aging meditators versus non-meditators.

Long-term meditation practitioners have also shown to have a higher tolerance for pain. [16] This effect has been correlated to altered function and structure in somatosensory cortices and an increased ability to decouple regions in the brain associated with the cognitive appraisal of pain (anterior cingulate cortex and dorsolateral prefrontal cortex). [17]

The brain state changes found in meditators are almost exclusively found in higher-order executive and association cortices. [14] This supports the notion that meditation increases self-regulation and attentiveness. Recent studies have also investigated how these changes may alter the functionality and connectivity of the default mode network, which is a hypothesized network of brain regions that are active when an individual is engaged in internal tasks such as daydreaming. [18]

Validity of findings

In the meta-analysis performed by Fox et al., several sources of bias were indicated which bring into question the validity of meditation studies which use neuroimaging. Fox et al. suggests a publication bias may be leading to the over-reporting of significant results. [19] Despite this, however, Fox et al. found "consistent differences in prefrontal cortex and body awareness regions" in "areas key to meta-awareness..., exteroceptive and interoceptive body awareness..., memory consolidation and reconsolidation..., self and emotion regulation..., and intra- and interhemispheric communication..." and that changes were significant with "moderate" global median effect size and "consistent and medium-sized brain structure differences." [19]

More research will be needed before any firm conclusions can be made.[ citation needed ]

Positive portrayal

Besides scientific literature, some authors have written of the promising research on meditation in books targeted for general audiences. One such book, Buddha's Brain by Rick Hanson, PhD shares the current scientific research and investigations into meditation. [20] Hanson, a neuroscientist and researcher, explains to readers the scientific studies in plain language and discuss the impact of the results. Hanson's main argument is that positive emotions, like love can be strengthened through meditation in a neuroplastic manner, citing dozens of scientific studies to support this claim. [20] Hanson's viewpoint is representative of a larger popular movement to study and embrace Eastern phenomena including meditation in the Western world.

Criticism

Critics, like Owen Flanagan, PhD, believe that Hanson, and those like him, are overextending the results of current scientific studies.[ citation needed ] In his book Bodhisattva's Brain: Buddhism Naturalized, Flanagan presents a more conservative viewpoint of current scientific research and cautions readers against the seemingly exciting results of recent studies. [21] Flanagan does not believe current science supports the idea that positive emotion can be strengthened in the same way that stroke victims can recover use of limbs with use. [21] Flanagan does acknowledge that meditation may be beneficial in some way, but the mechanism of how meditation affects the brain is still clouded. [21] Similarly, Awasthi argues that meditation is non-specific to the research studies showing clinical efficacy in some cases, though mechanisms remain unclear. [22] Flanagan and Hanson use many of the same scientific studies to attempt to support their differing viewpoint, but both authors identify the need and importance of future studies investigating meditation. Meditation research is still in its early stages and a lot more replicable results need to be established before the science community can back its efficiency.

See also

Related Research Articles

<span class="mw-page-title-main">Anterior cingulate cortex</span> Brain region

In the human brain, the anterior cingulate cortex (ACC) is the frontal part of the cingulate cortex that resembles a "collar" surrounding the frontal part of the corpus callosum. It consists of Brodmann areas 24, 32, and 33.

<span class="mw-page-title-main">Precuneus</span> Region of the parietal lobe of the brain

In neuroanatomy, the precuneus is the portion of the superior parietal lobule on the medial surface of each brain hemisphere. It is located in front of the cuneus. The precuneus is bounded in front by the marginal branch of the cingulate sulcus, at the rear by the parieto-occipital sulcus, and underneath by the subparietal sulcus. It is involved with episodic memory, visuospatial processing, reflections upon self, and aspects of consciousness.

<span class="mw-page-title-main">Insular cortex</span> Portion of the mammalian cerebral cortex

The insular cortex is a portion of the o cerebral cortex folded deep within the lateral sulcus within each hemisphere of the mammalian brain.

A gamma wave or gamma rhythm is a pattern of neural oscillation in humans with a frequency between 25 and 140 Hz, the 40 Hz point being of particular interest. Gamma rhythms are correlated with large scale brain network activity and cognitive phenomena such as working memory, attention, and perceptual grouping, and can be increased in amplitude via meditation or neurostimulation. Altered gamma activity has been observed in many mood and cognitive disorders such as Alzheimer's disease, epilepsy, and schizophrenia.

Alpha waves, or the alpha rhythm, are neural oscillations in the frequency range of 8–12 Hz likely originating from the synchronous and coherent electrical activity of thalamic pacemaker cells in humans. Historically, they are also called "Berger's waves" after Hans Berger, who first described them when he invented the EEG in 1924.

<span class="mw-page-title-main">Affective neuroscience</span> Study of the neural mechanisms of emotion

Affective neuroscience is the study of how the brain processes emotions. This field combines neuroscience with the psychological study of personality, emotion, and mood. The basis of emotions and what emotions are remains an issue of debate within the field of affective neuroscience.

<span class="mw-page-title-main">Posterior cingulate cortex</span> Caudal part of the cingulate cortex of the brain

The posterior cingulate cortex (PCC) is the caudal part of the cingulate cortex, located posterior to the anterior cingulate cortex. This is the upper part of the "limbic lobe". The cingulate cortex is made up of an area around the midline of the brain. Surrounding areas include the retrosplenial cortex and the precuneus.

<span class="mw-page-title-main">Mu wave</span> Electrical activity in the part of the brain controlling voluntary movement

The sensorimotor mu rhythm, also known as mu wave, comb or wicket rhythms or arciform rhythms, are synchronized patterns of electrical activity involving large numbers of neurons, probably of the pyramidal type, in the part of the brain that controls voluntary movement. These patterns as measured by electroencephalography (EEG), magnetoencephalography (MEG), or electrocorticography (ECoG), repeat at a frequency of 7.5–12.5 Hz, and are most prominent when the body is physically at rest. Unlike the alpha wave, which occurs at a similar frequency over the resting visual cortex at the back of the scalp, the mu rhythm is found over the motor cortex, in a band approximately from ear to ear. People suppress mu rhythms when they perform motor actions or, with practice, when they visualize performing motor actions. This suppression is called desynchronization of the wave because EEG wave forms are caused by large numbers of neurons firing in synchrony. The mu rhythm is even suppressed when one observes another person performing a motor action or an abstract motion with biological characteristics. Researchers such as V. S. Ramachandran and colleagues have suggested that this is a sign that the mirror neuron system is involved in mu rhythm suppression, although others disagree.

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<span class="mw-page-title-main">Effects of meditation</span> Surveys & evaluates various meditative practices & evidence of neurophysiological benefits

The psychological and physiological effects of meditation have been studied. In recent years, studies of meditation have increasingly involved the use of modern instruments, such as fMRI and EEG, which are able to observe brain physiology and neural activity in living subjects, either during the act of meditation itself or before and after meditation. Correlations can thus be established between meditative practices and brain structure or function.

<span class="mw-page-title-main">Electroencephalography</span> Electrophysiological monitoring method to record electrical activity of the brain

Electroencephalography (EEG) is a method to record an electrogram of the spontaneous electrical activity of the brain. The biosignals detected by EEG have been shown to represent the postsynaptic potentials of pyramidal neurons in the neocortex and allocortex. It is typically non-invasive, with the EEG electrodes placed along the scalp using the International 10-20 system, or variations of it. Electrocorticography, involving surgical placement of electrodes, is sometimes called "intracranial EEG". Clinical interpretation of EEG recordings is most often performed by visual inspection of the tracing or quantitative EEG analysis.

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<span class="mw-page-title-main">Resting state fMRI</span> Type of functional magnetic resonance imaging

Resting state fMRI is a method of functional magnetic resonance imaging (fMRI) that is used in brain mapping to evaluate regional interactions that occur in a resting or task-negative state, when an explicit task is not being performed. A number of resting-state brain networks have been identified, one of which is the default mode network. These brain networks are observed through changes in blood flow in the brain which creates what is referred to as a blood-oxygen-level dependent (BOLD) signal that can be measured using fMRI.

Pain empathy is a specific variety of empathy that involves recognizing and understanding another person's pain.

<span class="mw-page-title-main">Mechanisms of mindfulness meditation</span>

Mindfulness has been defined in modern psychological terms as "paying attention to relevant aspects of experience in a nonjudgmental manner", and maintaining attention on present moment experience with an attitude of openness and acceptance. Meditation is a platform used to achieve mindfulness. Both practices, mindfulness and meditation, have been "directly inspired from the Buddhist tradition" and have been widely promoted by Jon Kabat-Zinn. Mindfulness meditation has been shown to have a positive impact on several psychiatric problems such as depression and therefore has formed the basis of mindfulness programs such as mindfulness-based cognitive therapy, mindfulness-based stress reduction and mindfulness-based pain management. The applications of mindfulness meditation are well established, however the mechanisms that underlie this practice are yet to be fully understood. Many tests and studies on soldiers with PTSD have shown tremendous positive results in decreasing stress levels and being able to cope with problems of the past, paving the way for more tests and studies to normalize and accept mindful based meditation and research, not only for soldiers with PTSD, but numerous mental inabilities or disabilities.

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<span class="mw-page-title-main">Judson A. Brewer</span> American psychiatrist, neuroscientist and author

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Matthew D. Sacchet is an American neuroscientist and Assistant Professor of Psychiatry at Harvard University. At Massachusetts General Hospital, Sacchet directs the Meditation Research Program. His research focuses on advancing the science of meditation and includes studies of brain structure and function using multimodal neuroimaging, in addition to neurofeedback, clinical trials, and computational approaches. He is notable for his work at the intersection of neuroscience, meditation, and mental illness. His work has been cited over 4,500 times and covered by major media outlets including CBS, NBC, NPR, Time, and The Wall Street Journal. In 2017 Forbes Magazine selected Sacchet for the “30 Under 30”.

References

  1. ↑ Mizuno, Kogen (1972). Essentials of Buddhism. Tokyo: Kosei Publishing Company.
  2. ↑ Ahir, D.C. (1999). Vipassana : A Universal Buddhist Meditation Technique. New Delhi: Sri Satguru Publications.
  3. ↑ Kabat-Zinn, Jon (1998). Wherever You Go, There You Are : Mindfulness Meditation in Everyday Life. New York: Hyperion.
  4. ↑ Clark, Amelie. "Which Frequency/Hz Is Good For Meditation?". Incense Junction. Retrieved 16 August 2020.
  5. 1 2 3 4 Cahn BR, Polich J (2006). "Meditation states and traits : EEG, ERP, and neuroimaging studies". Psychological Bulletin. 132 (2): 180–211. doi:10.1037/0033-2909.132.2.180. PMID   16536641.
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  8. ↑ Holzel BK, Ott U, Hempel H, Hackl A, Wolf K, Stark R, Vaitl D (2007). "Differential engagement of anterior cingulate and adjacent medial frontal cortex in adept meditators and non-meditators". Neuroscience Letters. 421 (1): 16–21. doi:10.1016/j.neulet.2007.04.074. PMID   17548160. S2CID   3195263.
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  11. ↑ Stigsby B, Rodenberg JC, Moth HB (1981). "Electroencephalographic findings during mantra meditation (transcendental meditation). A controlled, quantitative study of experienced meditators". Electroencephalography and Clinical Neurophysiology. 51 (4): 434–442. doi:10.1016/0013-4694(81)90107-3. PMID   6164542.
  12. ↑ Becker DE, Shapiro D (1981). "Physiological responses to clicks during Zen, yoga, and TM meditation". Psychophysiology. 18 (6): 694–699. doi:10.1111/j.1469-8986.1981.tb01846.x. PMID   7031742.
  13. ↑ Andersen J (2000). "Meditation meets behavioural medicine: The story of experimental research on meditation". Journal of Consciousness Studies. 7: 17–73.
  14. 1 2 Fox, Kieran C.R.; Nijeboer, Savannah; Dixon, Matthew L.; Floman, James L.; Ellamil, Melissa; Rumak, Samuel P.; Sedlmeier, Peter; Christoff, Kalina (June 2014). "Is meditation associated with altered brain structure? A systematic review and meta-analysis of morphometric neuroimaging in meditation practitioners". Neuroscience & Biobehavioral Reviews. 43: 48–73. doi:10.1016/j.neubiorev.2014.03.016. PMID   24705269. S2CID   207090878.
  15. ↑ Pagnoni G, Cekic M (2007). "Age effects on gray matter volume and attentional performance in Zen meditation". Neurobiology of Aging. 28 (10): 1623–1627. doi:10.1016/j.neurobiolaging.2007.06.008. PMID   17655980. S2CID   16755503.
  16. ↑ Grant, J. A.; Rainville, P. (5 January 2009). "Pain Sensitivity and Analgesic Effects of Mindful States in Zen Meditators: A Cross-Sectional Study". Psychosomatic Medicine. 71 (1): 106–114. doi:10.1097/psy.0b013e31818f52ee. PMID   19073756. S2CID   14953679.
  17. ↑ Grant, Joshua A.; Courtemanche, Jérôme; Rainville, Pierre (January 2011). "A non-elaborative mental stance and decoupling of executive and pain-related cortices predicts low pain sensitivity in Zen meditators". Pain. 152 (1): 150–156. doi:10.1016/j.pain.2010.10.006. PMID   21055874. S2CID   24114284.
  18. ↑ Jang, Joon Hwan; Jung, Wi Hoon; Kang, Do-Hyung; Byun, Min Soo; Kwon, Soo Jin; Choi, Chi-Hoon; Kwon, Jun Soo (January 2011). "Increased default mode network connectivity associated with meditation". Neuroscience Letters. 487 (3): 358–362. doi:10.1016/j.neulet.2010.10.056. PMID   21034792. S2CID   8169221.
  19. 1 2 Fox, Kieran C.R.; Nijeboer, Savannah; Dixon, Matthew L.; Floman, James L.; Ellamil, Melissa; Rumak, Samuel P.; Sedlmeier, Peter; Christoff, Kalina (2014). "Is meditation associated with altered brain structure? A systematic review and meta-analysis of morphometric neuroimaging in meditation practitioners". Neuroscience & Biobehavioral Reviews. 43: 48–73. doi:10.1016/j.neubiorev.2014.03.016. PMID   24705269. S2CID   207090878.
  20. 1 2 Hanson, Rick (2009). Buddha's Brain: The Practical Neuroscience of Happiness, Love, and Wisdom . Oakland, CA: New Harbinger Publication, INC. ISBN   978-1572246959.
  21. 1 2 3 Flanagan, Owen (2011). Bodhisattva's Brain: Buddhism Naturalized. Cambridge, MA: The MIT Press. ISBN   978-0262016049.
  22. ↑ Awasthi B (2013). "Issues and perspectives in meditation research: in search for a definition". Frontiers in Psychology. 3: 613. doi: 10.3389/fpsyg.2012.00613 . PMC   3541715 . PMID   23335908.
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