The biology of meditation. How meditating can change your brain

Many of us are already familiar with what it means to meditate, in a broad sense, and we have often heard that meditation can improve our lives. Several books and articles have been written on the positive effects exerted by meditation on our bodies and minds. But what is the nature of meditation and how can it help us improve our mental states? More specifically, what happens at the level of neural networks, brain cells and molecules that results in all these beneficial actions upon meditating?

This being human is a guest house. Every morning a new arrival. A joy, a depression, a meanness, some momentary awareness comes as an unexpected visitor. Welcome and entertain them all! […] The dark thought, the shame, the malice. Meet them at the door laughing and invite them in. Be grateful for whatever comes. Because each has been sent as a guide from beyond.

The Guest House by Rumi. Translation by Coleman Barks

FIGURE 1 |Sigiriya rock located near the Dambulla town, in the Central Province, Sri Lanka. Own image.

An introduction to meditation ~ its styles and purposes

Meditation encompasses various emotional and attentional regulatory practices, which aim at improving an individual’s cognitive abilities. Many recent behavioral, electroencephalographic and neuroimaging studies have investigated the neuronal events related to meditation, in order to achieve an increased understanding of cognitive and affective neuroplasticity, attention and self-awareness, as well as for their possible clinical implications.

The video below shows the kind of brain changes meditation leads to, in a monk who is a long-term practitioner.

According to Raffone and Sirivasan (2010), a central feature of meditation is the regulation of attention, and as such, meditation practices can be classified into two main styles—focused attention (FA) and open monitoring (OM)—depending on how attentional processes are directed. While the FA (‘concentrative’) style is based on focusing attention on a given object in a sustained manner, the second style, OM (‘mindfulness-based’) meditation, involves the non-reactive monitoring of the content of ongoing experience. More specifically, mindfulness refers to being constantly aware of the way we perceive and monitor all mental processes, including perceptions, sensations, cognitions and affects.

FA meditation techniques imply, apart from sustaining the attention on an intended object, monitoring attentional focus, detecting distraction, disengaging attention from the source of distraction, and (re)directing attention (back) on the object. This kind of attentional stability and vividness is achieved through concentrated calmness or serene attention, denoted by the word Samatha (which literarily means quiescence) in the Buddhist contemplative tradition. Another technique which can be broadly included in the FA meditation is transcendental meditation, which centers on the repetition of a mantra.

Unlike FA meditation, OM meditation does not involve an explicit attentional focus, and therefore does not seem to be associated with brain areas that control sustained or focused attention. Instead, OM meditation engages brain regions implicated in vigilance, monitoring and detachment of attention from sources of distraction from the ongoing stream of experience. Therefore, OM meditation is based on detecting arising sensations and thoughts within an unrestricted ‘background’ of awareness, without a ‘grasping’ of these events in an explicitly selected focus. In the transition from a FA to an OM meditative state, the object as the primary focus is gradually replaced by an ‘effortless’ sustaining of an open background of awareness, without an explicit attentional selection. In the Buddhist tradition, the practice of Vipassana (insight) OM meditation requires, first of all, attentional stability and vividness (acuity), as developed in FA meditation, in order to achieve a deep and reliable introspection.

The ancient yogic practice of Yoga Nidra, which is less-known, and yet is becoming increasingly popular, can also fall into the category of OM meditation. It is said to reduce stress and improve sleep, and that it has the potential to engender a profound sense of joy and well-being.

Another type of OM meditation worth mentioning here is the loving-kindness meditation or non-referential compassion (also known as Mettā in the Pali language), which involves compassion-based mental training aimed at promoting empathy. Practicing this kind of meditation is believed to increase the capacity for forgiveness, connection to others and self-acceptance, and to boost well-being and reduce stress. For more detailed descriptions as well as a deeper and broader understanding of the neurological implications of these different meditation practices, I strongly encourage you to check out the reviews listed in the Reference section, especially Brandmeyer et al. (2019) and Raffone & Srinivasan (2010).

Of all these different kinds, mindfulness meditation, which originally stems from Buddhist meditation traditions, has received the most attention in neuroscience research over the last twenty years.

Research over the past two decades broadly supports the claim that mindfulness meditation — practiced widely for the reduction of stress and promotion of health — exerts beneficial effects on physical and mental health, and cognitive performance. 

Tang et al. (2015)

Sustained engagement with mindfulness meditative practices has been shown to have neurophysiological and psychological benefits. In healthy individuals, several months of mindfulness meditation practice correlates with improvements in self-regulation and subjective well-being. Even much shorter mindfulness meditation training, of a few days, has a positive impact on mood and executive functioning, while at the same time reducing fatigue and anxiety.

Brain structural changes following mindfulness meditation

Several recent studies have investigated the structural changes in the brain related to mindfulness meditation, and have reported alterations in cortical thickness, hippocampal volume, and grey-matter volume and/or density. However, before we dive into how meditation can change our brains, it should be mentioned that there are a few issues with the current state of meditation research. First of all, most of these studies have made cross-sectional comparisons between experienced meditators and controls. But only a few recent studies have investigated longitudinal changes in novice practitioners. These logitudinal studies are very important because they follow subjects over a long-term period of practice, and are thus able to determine whether changes induced by meditation training persist in the absence of continued practice. Therefore, more such studies would be required for a complete picture of the effects of meditation on mental health.

In addition, the studies on mindfulness meditation so far have generally included small sample sizes, of between 10 and 34 subjects per group, which leads to limitations in interpreting the results, as well as increases the chances of false-positives. Another prossible issue is that these studies use different research designs, measurements and type of mindfulness meditation. Hence, it comes as no surprise that the reported effects of meditation are diverse and cover multiple regions in the brain, including the cerebral cortex, subcortical grey and white matter, brain stem and cerebellum. That being said, these findings can also reflect the fact that the effects of meditation involve large-scale and interactive brain networks.

According to various fMRI studies, minfulness meditation exerts its effects primarily (though not exclusively) on a network of brain regions – the Default Mode Network (DMN). This network comprises structures in the medial prefrontal cortex (PFC), posterior cingulate cortex (PCC), anterior precuneus and inferior parietal lobule, which have been previously shown to have high activity during rest, mind wandering and conditions of stimulus-independent thought. These regions have been suggested to support different mechanisms by which an individual can ‘project’ themselves into another perspective.

When comparing meditators with naïve subjects, DMN regions, such as the medial PFC and PCC, have shown much less activity in meditators, across different types of meditation. This has been interpreted as indicating diminished self-referential processing. Experienced meditators also seem to exert stronger coupling between the PCC, dorsal anterior cingulate cortex (ACC) and dorsolateral PFC, both at baseline and during meditation, which indicates stronger cognitive control over the function of the DMN.

Brewer et al. (2011) investigated brain activity in experienced meditators versus meditation-naïve controls as they performed several different mindfulness meditations (Concentration, Loving-Kindness, Choiceless Awareness). They found that the main nodes of the DNM (medial PFC and PCC) were relatively deactivated in experienced meditators across all meditation types (Figure 2). Moreover, functional connectivity analysis revealed increased coupling in experienced meditators between the PCC, dorsal ACC, and dorsolateral prefrontal cortices, both at baseline and during meditation, as seen in Figure 3. This increased connectivity with medial PFC regions supports greater access of the default circuitry to information about internal states, because this region is also highly interconnected with limbic regions (such as insula and amygdala).

FIGURE 2 | Experienced meditators demonstrate decreased DMN activation during different meditation conditions: Choiceless Awareness (green bars), Loving-Kindness (red), and Concentration (blue) meditations. The decreased activation in PCC in meditators is common across different meditation types. Brain activation in meditators > controls is shown, collapsed across all meditations, relative to baseline (A and B). Activations in the left mPFC and PCC (C and D). Taken from Brewer et al. (2011)

FIGURE 3 | Experienced meditators show coactivation of mPFC, insula, and temporal lobes during meditation. Differential functional connectivity with mPFC seed region and left posterior insula is shown in meditators > controls: (A) at baseline and (B) during meditation. (C) Connectivity z-scores (±SD) are shown for left posterior insula. Choiceless Awareness (green bars), Loving-Kindness (red), and Concentration (blue) meditation conditions. Taken from Brewer et al. (2011)

Meditators also reported significantly less mind-wandering, which has been previously associated with activity in the DMN. Therefore, these results demonstrated that alterations in the DMN are related to reduction in mind-wandering. They also suggested that meditation practice may transform the resting-state experience into one that resembles a meditative state – a more present-centered default mode.

The findings from this study have several clinical implications, given that a number of pathological conditions have been associated with dysfunction within areas of the DMN, including depression. The self-referrential function of the DMN has pointed to the possibility that excessive rumination (negative inner preoccupation about the personal past, present and future) in depression involves excessive DMN activity as well as an inability to switch out of it, in response to external demands. Mindfulness meditation may prove useful in reducing distractive and ruminative thoughts and behaviors, and this ability may provide a unique mechanism by which mindfulness meditation reduces distress and improves mood.

In addition, meditation has also been shown to promote neuroplasticity, an important neuronal process that entails structural and functional brain adaptations in response to changes in environmental conditions. A key neurotrophin that promotes neuroplasticity is the brain-derived neurotrophic factor (BDNF), which is usually found in abnormally low levels in various psychiatric and neurological disorders. Meditation has been shown to increase the levels of BDNF, thus promoting neuronal development, survival and plasticity, which in turn contribute to restoring the normal functioning of brain networks.

In sum, there is emerging evidence that mindfulness meditation might trigger neuroplastic changes in brain regions involved in the regulation of emotion and cognition. Although, as mentioned earlier, these studies often suffer from low methodological quality and present with speculative post-hoc interpretations, this is quite common in a new field of research. Thus, further research needs to use longitudinal, randomized and actively controlled research designs and larger sample sizes, as well as to concentrate on the biological factors implicated in mental health, in order to advance the understanding of how mindfulness meditation interacts with the brain. If supported by rigorous research, the practice of mindfulness meditation might be a promising therapeutic approach for clinical disorders, such as depression, and might facilitate the cultivation of a healthy mind and improved well-being.

For the readers interested in the effects of meditation on depression, please visit my article The biological implications of meditation practices in the treatment of depression.

References

  • Brandmeyer, T., Delorme, A., Wahbeh, H. (2019). Chapter 1 – The neuroscience of meditation: classification, phenomenology, correlates, and mechanisms, Editor(s): Narayanan Srinivasan, Progress in Brain Research, Elsevier, 244: 1-29. doi: org/10.1016/bs.pbr.2018.10.020
  • Brewer, J.A., Worhunsky, P.D., Gray, J.R., Tang, Y.Y., Weber, J., Kober, H. (2011). Meditation experience is associated with differences in default mode network activity and connectivity. Proc Natl Acad Sci U S A, 108(50):20254-9. doi: 10.1073/pnas.1112029108
  • Kabat-Zinn, J. (2003). Mindfulness-based interventions in context: past, present, and future. Clin Psychol Sci Pract 10:144–156
  • Heuschkel, K., & Kuypers, K.P.C. (2020). Depression, Mindfulness, and Psilocybin: Possible Complementary Effects of Mindfulness Meditation and Psilocybin in the Treatment of Depression. A Review. Front. Psychiatry, 11:224. doi: 10.3389/fpsyt.2020.00224
  • Raffone, A., & Srinivasan, N. (2010). The exploration of meditation in the neuroscience of attention and consciousness. Cognitive Processing, 11:1-7. doi: 10.1007/s10339-009-0354-z.
  • Tang, Y.Y., Hölzel, B.K., Posner, M.I. (2015). The neuroscience of mindfulness meditation. Nat Rev Neurosci, 16(4):213-25. doi: 10.1038/nrn3916
  • Zeidan, F., Johnson, S., Diamond, B., David, Z., & Goolkasian, P. (2010). Mindfulness meditation improves cognition: Evidence of brief mental training. Consciousness and Cognition, 19, 597-605. doi: org/10.1016/j.concog.2010.03.014.

Oxytocin and Social Bonding

While most of us would be able to describe what being affectively close to someone feels like, we might find it harder to explain why and how such a connection forms.

Why do we love and what makes us love certain people? Why is love so different depending on the subject of our affection? Is it possible to measure love? What does the complete absence of love in an individual reveal about their health state? With so many questions having been formulated throughout centuries, no wonder love has become a universal conundrum. Traversing various disciplines, it not only represents the realm of the literary, but it has increasingly become one of the central focuses in philosophy, biology, social sciences and neuroscience.

As far as the neuroscientific approaches to love go, this concept is represented by affiliative bonds. Therefore, from now on we shall refer to love as such. For the sake of the reader’s personal interest, we shall further discuss affiliative interactions as they appear and manifest in humans. Affiliation describes the ability of an individual to form close interpersonal bonds with other individuals of the same species. Three prototypes of affiliation have been identified: parental (between children and their parents), pair (between romantic partners) and filial (between friends).

This article is intended to introduce the reader to the evolutionary significance and neurochemical mechanisms underlying social bonding/affiliation. As such, the above-mentioned types of affiliative behaviours will be only in part separately discussed. Instead, we shall focus on what these categories share in common, particularly, the hormone-neurotransmitter oxytocin and the concept of synchrony.

Synchrony refers to the process by which the members of a social group collaborate with each other, in order to achieve a social goal. This kind of collaboration involves concordance in time between members, at the level of behaviour and physiological processes (e.g. hormonal release, neural firing). Through these synchronous processes underlying social reciprocity, each member is introduced to the social milieu, becomes adapted to his/her environment and learns how to survive.

Intimate reciprocal relationships between two individuals in a social group help shape the individual’s moral, empathic and pro-social orientation, as well as social adaptation and self-regulation. The interaction between mother and infant is critical to the social maturation and well-being of the young. Human mothers, just like other mammals, exhibit specific postpartum behaviours, such as affectionate touch, high-pitched vocalisations, expressing positive affect, which lead to the notoriously strong mother-infant bond.

This type of specific attachment relationship coordinates the physiology of the infant with the behaviours of the mother. Moreover, this mother-infant synchrony enables the temporal alignment of the infant’s inner state with the responses of the social environment (via the mother). The absence of a proper interaction between mother and child, especially within the critical period (between 3 and 9 months after birth), has been shown to contribute to the development of autism spectrum disorders (for more information on autism, check out this previous article – Decoding autism).

Romantic attachment is another type of social bonding in humans, with significant implications to the normal psychological functioning of the individual. According to recent studies, both parental and romantic relationships share similar behavioural characteristics (gaze, touch, affects, vocalisations and coordination of these behaviours between the members of the pair) and rely on similar neuroendocrine mechanisms. These mechanisms mainly involve a nine amino-acid neuropeptide known as oxytocin.

Oxytocin acts as both a hormone and a neurotransmitter. It is associated with a variety of functions including the initiation of uterine contractions during parturition, homeostatic, appetitive and reward processes, and last but certainly not least, the formation of affiliative bonds. For the latter, oxytocin plays a very important role in social recognition, maternal behaviour and development of partner preferences.

Oxytocin is produced in the hypothalamus, by the magnocellular neurones clustered in two types of nuclei: the supraoptic and paraventricular. These neurones send projections to the posterior pituitary gland, thus engaging the oxytocin system with the hypothalamic-pituitary-adrenal axis, mediating the stress response, as well as parturition, lactation and milk ejection. Other projections from the paraventricular nucleus go to various forebrain limbic structures (e.g. amygdala, hippocampus), brainstem (e.g. ventral tegmental area) and spinal cord. There are also other areas, apart from the brain and spinal cord, which receive oxytocin signalling, such as the heart, gastrointestinal tract, uterus, placenta, testes etc. With such extensive projections, it comes as no surprise that oxytocin is involved in a wide variety of processes.

In romantic and parental attachment, oxytocin induces the motivation to initiate sexual behaviour, the formation of sexual preferences and the increased stimulant value of the infant for its mother, via its connectivity with the mesolimbic dopaminergic neurones. The neurotransmitter dopamine plays a major role in the reward-motivated behaviour. Therefore, the oxytocin-dopamine interaction is key to the motivation to bond between members of romantic or child-parent relationships.

If you were wondering why the parental attachment has so far been presented only from the perspective of the mother-child relationship, that is because in males a different hormone mediates parental behaviour. Vasopressin can be seen as the male equivalent of oxytocin, as it modulates affiliation, aggression, juvenile recognition, partner preference and parental behaviour in males. Having said that, there are studies which show that oxytocin also supports paternal behaviour and is linked to the father-typical affiliative behaviour.

Oxytocin is also very important in establishing close connection with our best friends (what is known as filial attachment). According to research in this area, children start showing selective attachment to a ‘best friend’ around the age of 3. This kind of interpersonal interaction represents the first attachment to non-kin members of society, therefore, a crucial step in the normal development of any human being.

Depending on the level of synchronous parenting children experienced during infancy, their interactions with best friends can vary in the degree of reciprocity, emotional involvement and concern for the friend’s needs. These behaviours are modulated by oxytocin. During the first 3 years of life, oxytocin secretion in humans depends on the parent’s postpartum behaviour (which is predicted by the parents’ own levels of oxytocin) and, in turn, determines the degree of empathy between close friends. Therefore, a reasonable assumption, which has been recently proven, is that children benefiting from high parental reciprocity during infancy develop better social adaptation, are more friendly and cooperative, and show greater empathy.

All in all, the social bonds we form with members of our social group, be they our family, romantic partners or friends, are dependent on certain hormones and behaviours occurring at critical stages of development. Close attachment bonds with our parents, during early infancy, are later translated into affiliations to non-kin members of the social groups, who we come across during childhood, evolving into intimate friendships during adolescence, which eventually shape the ability of the adult human to form and maintain romantic connections and provide nurture for the next generation.

What we have just discussed is of importance for different aspects. Focusing on oxytocin and synchrony provides better understanding of neurodevelopmental disorders such as autism. At the same time, this focus offers some answers to questions regarding the reasons and mechanisms underlying the many types of love us humans experience throughout our lives.

References

Feldman, R. (2012). Oxytocin and social affiliation in humans. Hormones and Behavior, 61(3),  380-391. 

Hammock, E. A. ., & Young, L. J. (2006) Oxytocin, vasopressin and pair bonding: implications for autism. Philosophical Transactions of the Royal Society B: Biological Sciences, 361(1476), 2187–2198. 

Even flies sleep and learn

Sleep is a fascinating process that allows most of the creatures on Earth to function at their normal capacity and survive the environmental challenges. Recent theories support the idea that one of the main functions of sleep is not energy conservation or tissue restoration, as previously thought, but actually, enhancement of brain function. Sleep appears to be involved in consolidation of memories and improvement of learning. As you probably remember from the previous article, there are essentially to phases of sleep: REM and non-REM. The latter has been shown to be involved in consolidation of both declarative and non-declarative memories, whereas REM sleep is believed to enhance the formation of procedural and emotional (non-declarative) memories.

If you’ve ever wondered whether insects can sleep or not, the answer is yes. Several studies in Drosophila melanogaster , the fruit fly famous for Morgan’s discoveries of chromosomal inheritance, proved these flies have periods of ‘rest’. During rest , Drosophila stops moving and becomes more difficult to be aroused, which resembles what we understand by ‘sleep’. Moreover, it appears that these flies can form short-term and long-term memories, especially revealed by studies of olfactory associative conditioning. Surprising, isn’t it? Even though it is known that insects have brains, they seem too primitive, at a first glance, for complex cognitive functions such as memory and learning. Well, it’s obvious that insects are much smarter than we thought.

What’s more stunning is that, in Drosophila, just as in humans, sleep has evident effects on long term memory formation and sleep deprivation can dramatically affect this function. According to several studies, sleep homeostasis positively influences learning. During non-REM sleep, the brain shows slow oscillatory activity, which is characterised by waves of action potentials with low frequency and high amplitude. These slow waves are controlled by homeostatic processes and increase after learning tasks. Hence, sleep, which induces slow wave activity, plays a very important role in enhancing learning performances.

The homeostatic control of sleep has been somewhat elucidated by studies in our old friend, Drosophila. Organisms need not only a circadian clock (which sets a day-night rhythm, synchronising the body with the environment), but also a homeostatic system, which regulates sleep according to prior wakefulness. Just like in the circadian system, the homeostatic system seems to be genetically regulated and, eventually, resulting from neuronal activity.

Specialised sleep-promoter neurones in Drosophila, called the dorsal fan-shaped body (FB) neurones, become excited when the organism is sleep-deprived and fire action potentials (which can be surprising, given that non-REM sleep triggers reduced brain activity). It is not exactly known how the nervous system can sense lack of sleep, but it is believed that substances such as adenosine and unfolded proteins, released after prolonged wakefulness, are potential signals. Thus, after detecting too much wakefulness, dorsal FB neurones become excited and promote sleep. The gene that controls the function of the dorsal FB neurones is the crossveinless-c (cv-c) gene, which encodes for a protein that regulates different ion channels (especially potassium channels), leading to changes in electrical conductance and the excitability of the sleep-promoter neurones.

 Just to give some more information and (possibly) complicate things a bit more, another link between sleep and long term memory is represented by the notch receptors, which have been found to be involved in the restoration of long term memory formation after sleep deprivation. Their main function is to influence the development of the nervous system in the embryo, but they also play a role in memory formation.

 As you have probably figured out by now, it is quite hard to have a complete picture of what sleep is about and how it can influence memory and learning. However, scientists are doing their best to shed some light on these wonderful phenomena. And before you close this page, don’t forget an important point: even something small like the fruit fly is able to sleep and learn!

I’d like to thank my friends Parnian Doostdar and Lee Chi Yu for sending me most of the materials I used for this article.

For further information:

Article 

Ackermann, S., Rasch, B., 2014. Differential effects of non-REM and REM on memory consolidation, Current neurology and neuroscience reports, vol. 14, p. 430

Donlea, J. M., Pimentel, D., Miesenbock, G., 2014. Neuronal machinery of sleep homeostasis in Drosophila. Neuron, vol. 81, pp. 860-872

Huber, R., Ghilardi, M. F., Massimini, M., Tononi, G., 2004. Local sleep and learning. Nature, vol. 430, pp. 78-81

Some mentions about the latest topic

Some of you have emailed me asking about what things we should stay away from during pregnancy, in order to avoid changing the normal course of a baby’s development. If you remember from the article about gender identity and sexual preferences see here, one of the most important factors in an individual’s development is represented  by sex hormones like androgens and oestrogen. They begin acting on our bodies in early pregnancy and even slight modifications in their functioning may dramatically affect our personality, preferences and behaviour as adults. 

Given external factors can greatly influence these hormones, it is very important to know which ones fall into the category of risk factors and therefore possibly affect our development. As expected, these factors pose a threat during pregnancy, which is why pregnant women should be particularly cautious about their life style. 

It has been suggested that taking aspirin while pregnant might increase the chance of the mother giving birth to a “more masculinised girl”. This is due to the actions of aspirin as a cyclooxygenase inhibitor; cyclooxygenase enzyme converts arachidonic acid into prostaglandins which apart from their well-known role in immune reactions, also seem to be involved in sexual behaviour. A decrease in the production of these compounds in female rats is thought to account for their man-like behaviour. 

Other factors that present a risk of having a lesbian daughter are smoking and synthetic drugs. The exact mechanisms of their actions is still unclear and it might turn out that they are not in fact such a threat. But it’s always better to prevent something rather than be oblivious to it. 

Also, stress during pregnancy can induce homosexuality in children, due to raised levels of cortisol which affects the production of sex hormones. So women caring a baby should try to stay as calm and relax as possible, even though that sounds like such a hard task especially when you’re pregnant! 

If you have any other questions or you would like to add your thoughts to this post, do not hesitate to leave a comment.