Meditation Brain Review

Effects of meditation on the brain — a review Pankaj Gupta May 10, 2008

1

Introduction

This paper reviews the state of scientific research on the effects of the ancient mental process of meditation on the physiology of the brain. It first defines meditation, as it was originally laid out in ancient religious Hindu and Buddhist texts (an explanation of the various types of meditation in Hinduism and Buddhism is beyond the scope of this paper but an overview of the most common forms is presented). Next, the paper presents more recent scientific definitions of the term. The paper then reviews observations published in scientific studies about the measured brain activity of practitioners while they are in meditation as well as when they are not. As we will see in the paper, the last few years have been especially illuminating on the subject, aided by new technologies such as functional magnetic resonance imaging (fMRI) as well as perhaps better access to experienced meditation practitioners (such as Tibetan monks) for research. Even so, it is important to note that this field is still in its infancy. Though studies so far have verified the positive effects of meditation of the brain under study, we are nowhere near either scientif-

1

ically proving or disproving the extraordinary claims about the positive effects of meditation mentioned in most spiritual texts on meditation. The potential benefits of such studies, as often mentioned in the papers themselves, are immense. Hopefully, with the weight of accepted scientific reason behind it, meditation and mental fitness may come more into our mainstream lives and not just into the mystical realm that it mostly occupies today, perhaps as physical fitness has become.

2

What is Meditation?

Meditation is a broad term encompassing a variety of techniques and practices, all relating to the mind. It is found in most religions today in various forms and seems to have been practised for at least 5000 years [Wikipedia]. Scriptures of early Hinduism describe a process called dhyana as one of the various forms of yoga, the path to spiritual mastery. Meditation is also central to Buddhism (Buddha himself is said to have gained enlightenment after deep meditation).1 Indeed, meditation probably forms the core of no other religion today as much as it does of most forms of Buddhism.

2.1

Meditation as described in Hindu and Buddhist texts

The ancient Hindu texts warn a practitioner (called a yogi) that dhyana is a difficult and long journey with the aim of achieving complete control of one’s mind on the path to spiritual awakening (nirvana). The journey starts from first trying to grasp 1

Zen is Japanese pronunciation of Chan, which is Chinese pronunciation of the Sanskrit Dhyana.

2

that the mind is distinct from one’s self. This is achieved by simply observing the mind and its “wanderings” (i.e., myriad thoughts sprouting in the mind) in silence for a period of time (few minutes to many hours every day, typically while sitting in an erect posture). The next step is to try to rein in those wanderings, by practicing continuous and intense focus on nothing but one chosen object. This object could be a sacred word2 or an image or one’s breath or a part of one’s own body (e.g., the area between one’s brows). The instruction is to not forcibly curb the thoughts from appearing in one’s mind but to simply observe them and gently let the mind come back to the intended object of attention. Even a little success in the beginning in this step typically reinforces in the practitioner that indeed the mind can be controlled and that it possibly could be distinct from oneself, because if this were not the case, then it would not be possible to observe the mind’s distraction and to bring it back. With time and practice, the mind begins to wander less and the effort required to bring it back decreases. The next step for a yogi is to gradually eliminate even the object of attention so that the mind is not focused on anything at all. This is somewhat mystically referred to as the void (shunya). It is said that when the mind is empty, the yogi can enter a higher level of consciousness wherein s/he experiences in full his or her body and mind from one moment to another. Buddhism apparently built upon the Hindu yogic form of meditation and developed its own forms. One such form is compassion meditation. In this, the ultimate stated aim is to generate unconditional love and compassion for every being. The instruction to the novice is to think of a loved one (such as family member or 2

For example, OM is a Hindu sacred syllable often used in both chants and as an object of concentration.

3

friend) and wish them kindness, love and freedom from suffering. Over time, the meditator attempts to expand this loving-kindness feeling towards all beings, thus generating a feeling of compassion at all times. Another important form is the Vipassana form of Meditation, referred to sometimes as insight meditation, described as a way of self-transformation through self-observation and introspection. This form may be quite similar to the final step of the yogic meditation described above.

2.2

Scientific definitions of meditation

Given the mystical origins of meditation, there are many challenges in coming up with a scientifically workable definition. Lutz et al. [2008b] do a wonderful job of this – defining two forms of meditation. First form is focused-attention meditation, where attention is sought to be maintained on a single object, and the second form is open-monitoring meditation where the focused-attention meditator’s object of attention is removed and the practitioner is instructed to continuously monitor the sum total (“stream”) of experience from moment to moment – or in the words of the paper: “Nonreactive awareness of automatic cognitive and emotional interpretations of sensory, perceptual and endogenous stimuli”. These two forms are identical to the second and third steps of yogic meditation mentioned above in Section 2.1. Frankly, while the scientific definition of focused-attention meditation still seems understandable to the uninitiated, the meaning of open-monitoring meditation seems difficult to grasp.3 Focused-attention meditation is also referred to as concentration meditation 3

As indeed warned by the meditation texts that such a process is very difficult to comprehend intellectually and may be only be experienced!

4

in literature, e.g., by Brefczynski-Lewis et al. [2007].

3

Effects of Meditation

Lutz et al. [2008b] break down the skills required in focused-attention meditation to: (1) maintaining attention, (2) monitoring attention, while detecting any distractions, and (3) ‘releasing’ the distraction and re-engaging attention on the focused object; and the skills required in open-monitoring meditation to: (1) nonreactive monitoring, especially of one’s emotional experiences as well as of one’s own body experiences, and (2) not focus attention on a single object. As we will see below, research show heightened activity in the respective areas of brain generally associated with that skill. In addition, there are several interesting observations made by such studies.

3.1

High activity in the attentional network in the brain during concentration meditation

In a controlled, functional magnetic resonance imaging (fMRI) based study of both expert and novice focused-attention meditators meditating on a fixed dot, Brefczynski-Lewis et al. [2007] indeed detect heightened activity during meditation in those parts of the brain that neuroscientists usually associate with attentional processing. This is a large overlapping network in the brain: the frontal parietal regions, lateral occipital, insula, multiple thalamic nuclei, basal ganglia, and cerebellar regions. Only novices showed negative activation (i.e., less activation in meditation than when at rest) in anterior temporal lobe bilaterally. The skills men-

5

tioned above needed for focused-attention meditation indeed showed up – specifically, the processes of engaging attention (visual cortex, as the study involved gazing a visual, a dot in this study), monitoring attention and conflict (dorsolateral prefrontal cortex and the dorsal anterior cingulate cortex), and attentional orienting (e.g., the superior frontal sulcus and intraparietal sulcus). Expert meditators showed more activity than novice meditators in multiple attentional and other regions including frontoparietal regions, cerebellar, temporal, para-hippocampal, and posterior occipital cortex, likely including the foveal visual cortex of the attended dot. Novice meditators showed more activation than experts in medial frontal gyrus/anterior cingulate and in the right mid-Insula to Posterior Insula – these regions have otherwise been shown to be negatively corelated with performance in a sustained attention task.

3.2

Gaining effortlessness with practice

It was also observed that the extent of the neural activity is generally proportional to the expertise of the meditator, but interestingly the activity tails off in highly experienced meditators. In other words, the activity in these parts of the brain shows an inverted U-shaped curve when plotted against the number of hours of practice behind a meditator. Specifically, Brefczynski-Lewis et al. [2007] report that expert meditators with more than 19,000 hours of meditation in their life showed more activation than novice meditators, while those with more than 44,000 hours showed less. This can be understood intuitively, as in the beginning, these parts of the brain get more active as they are exercised more and more resulting in increased activity.

6

However, with extensive experience, it becomes ‘effortless’ to maintain the same level of attention – thus reducing activity in these parts. This was reinforced by the paper above by also observing the hemodynamic response function in these parts of the brain. Expert meditators with most experience showed a “meditative startup increase” in hemodynamic activity at the beginning of meditation that fell back to baseline levels quickly (10-20s) after the beginning of the meditative state. On the other hand, other meditators showed a sustained hemodynamic response over the course of meditation. If the hemodynamic response is influenced by effort, experts clearly achieved effortless meditative state much quicker than the others in the study.

3.3

Reduced activity in brain regions involved with distraction

Brefczynski-Lewis et al. [2007] also provided a variety of distractor sounds of different valence (positive, neutral, negative) to meditators while they were in meditation. The study showed decreased activity in the right amygdala, medial frontal gyrus/anterior cingulate, and posterior cingulate in the experts, and in fact a negative correlation in the activity of these regions with the expertise of the meditator. As these regions are associated with emotional reactivity, this observation leads to the idea that focused-attention meditation leads to at least a partial “deautomatization” of the mental processes that interpret perceptual stimuli. This effect is heightened further in open-monitoring meditators. In the Vipassana tradition of Buddhist meditation, a device used to aid open-monitoring meditators is to do verbal labeling of their moment to moment experience. Stud-

7

ies[Hariri, 2000, Lieberman, 2007] have shown that this activates the right ventrolateral prefrontal cortex and attenuates responses in the amygdala through activity in the ventro-medial prefrontal cortex. This points to “better emotion regulation in open-monitoring meditators through processes instantiated in the ventral prefrontal cortex and inhibition of regions involved in automatic affective responses in appraisal systems, diminishing their intensity and duration”[Lutz et al., 2008b].

3.4

Increased activity in the affective response network in loving-kindness-compassion meditation

Lutz et al. [2008a] studied meditators involved in the practice of compassion meditation with a view to understand how training of such a process could affect the emotional and affective network of the brain. They took two groups – expert and novice – of meditators and asked them to be in two alternating states – meditation and rest – while they present emotional vocalizations (through human sounds) of three valences: positive, neutral and negative. They indeed found an increased activity in the regions of the brain underlying emotions and feelings (insula, anterior cingulate cortex (ACC), and possibly somatosensory areas), particularly in response to the negative emotional vocalizations made. Comparison between meditation and rest states between experts and novices also showed increased activation during meditation in amygdala, right temporoparietal junction, and right posterior superior temporal sulcus in response to all sounds, suggesting, greater detection of the emotional sounds and enhanced “mentation” about the mental states of others in experts.

8

3.5

Long term effects of meditation training

• Enduring alteration of the ’baseline’ or ’default mode’ of brain functioning, particularly in terms of improving the quality of attention and sustaining it on an object or a task. For example, Davidson and Lutz [2008] mention that meditation might help to reduce “neural noise”, and thus enhance signal-tonoise ratio in certain types of tasks. • In a fascinating study, Slagter et al. [2007] report increased efficiency of information processing by open-monitoring meditators, highlighting that such meditators have improved ability to not “get stuck” on one thing. They conduct experiments on a group of meditators (practitioner group) that had recently undergone 3 months of intensive Vipassana open-monitoring meditation (10-12 hours of meditation per day) and another novice group interested in meditation, but not having undergone any training. The experiments consist of flashing before the participants a series of images of random 15-19 letters, each letter shown for 50ms followed by 34 ms of blank followed by the next letter. Interspersed in this stream of letters are two digits, called “targets” T1 and T2. In one experiment, these targets are spaced by 336ms “short interval”) and in the other experiment, they are spaced by 772ms (“long interval”). Both experiments were conducted for the two groups before and after the 3 month training period of the practitioner group. After all the images were shown, the participant was asked to recall the first and the second target. The idea was to detect the influence of open-monitoring meditation on the “attention-deficit” blink. This is the amount of time needed by the brain to make sense of something before it can process another stim9

ulus and make sense of it. While certainly not an immutable number and generally varying among individuals, an attention deficit of around 500ms is common. Slagter et al. [2007] observed statistically significant differences in the abilities of the participant group and the novice group after the former’s intensive training. They found that all the 17 members of the participant group but 16 out of 23 members of the novice group were able to correctly detect T2. (Before the start of the meditation, both groups had almost identical rates of accurate T2 detection). The paper attributes this to reduced attentional resources required by T1 as a result of meditation, and confirms that by detecting smaller value at the time of T1 capture of P3b, a brain potential index of resource allocation. This further supports the idea that meditation could be used to train the brain to develop greater efficiency of information processing. • Potential impact on peripheral biological processes important for physical health, e.g., cortisol or immune function as reported by some clinical studies[Davidson, 2003, Carlson, 2007]. More studies are needed to support such claims. • Long term meditators can allegedly generate more stable and reproducible mental states. In addition, some researchers claim that long term meditation can lead to increased efficiency of basic mental functions such as attention and emotion reactivity in daily life. More longitudinal studies on the same individuals over time are needed to substantiate such claims.

10

4

Conclusions

Many researchers have commented that their observations show that at the very least many subcomponents of attention are trainable using meditation. This is in fact a remarkable statement. It may provide an answer to question posed by James [1890] more than a century ago when he asked how we might educate attention because such education would be “the education par excellence’. Expert practitioners of meditation have, for thousands of years, extolled the amazing positive effects of meditation (see, for example, Gupta and Rajpal, a twopart video interview taken by me of an expert practitioner). In this paper, we saw how recent scientific studies have – using accepted scientific practices of controlled experimentation and logical argumentation based on observations made in the laboratory – pretty much verified that these effects do show up in the meditators’ brains in a manner consistent with what we know of the brain today from other non-meditation related studies. It is clear to me that if one believes even any one of these three sources: (1) scientific studies, (2) self-reports of expert meditation practitioners, or (3) claims recorded in the ancient Hindu and Buddhist texts; one has to conclude that meditation is an immensely powerful process of transforming one’s brain, and indeed one’s self, for the better. It is therefore easy to predict that in the near future neuro-scientific studies of meditation will continue to get attention and patronage, hopefully helping bring meditation into the mainstream, and, who knows, possibly into the school syllabus of future generations.

11

References J. A. Brefczynski-Lewis, A. Lutz, H. S. Schaefer, D. B. Levinson, and R. J. Davidson. Neural correlates of attentional expertise in long-term meditation practitioners. Proceedings of the National Academy of Sciences, 104(27):11483–11488, 2007. L.E. et al. Carlson. One year pre-post intervention follow-up of psychological, immune, endocrine and blood pressure outcomes of mindfulness-based stress reduction (mbsr) in breast and prostate cancer outpatients. Brain Behav. Immun., 21:10381049, 2007. R.J. Davidson and A. Lutz. Buddha’s brain: Neuroplasticity and meditation. IEEE Signal Processing, 25(1):171–174, 2008. R.J. et al. Davidson. Alterations in brain and immune function produced by mindfulness meditation. Psychosom. Med., 65:564–570, 2003. Pankaj Gupta and Raman Rajpal. perienced

meditator.

A two part interview of an ex-

http://video.google.com/videoplay?docid=

-6994132063912771031&hl=en. A.R. et al. Hariri. Modulating emotional responses: effects of a neocortical network on the limbic system. Neuroreport, 11:43–48, 2000. W. James. The principles of psychology. Classics of Psychiatry and Behavioral Sciences Library, 1890. M.D. et al. Lieberman. Putting feelings into words: affect labeling disrupts amygdala activity in response to affective stimuli. Psychol Sci, 18:421428, 2007. 12

A. Lutz, J. A. Brefczynski-Lewis, T. Johnstone, and R. J. Davidson. Voluntary regulation of the neural circuitry of emotion by compassion meditation: Effects of expertise. PLoS One, 3(3):171–174, 2008a. A. Lutz, H. A. Slagter, J. Dunne, and R. J. Davidson. Attention regulation and monitoring in meditation. Trends in Cognitive Sciences, 12(4):163–169, 2008b. H. A. Slagter, A. Lutz, L. L. Greischar, A. D. Francis, S. Nieuwenhuis, J. M. Davis, and R. J. Davidson. Mental training affects use of limited brain resources. PLoS Biology, 5(6), 2007. Wikipedia. http://en.wikipedia.org/wiki/Meditation.

13