Is meditation associated with altered brain structure?

Fox, K. C., et al. (2014). Is meditation associated with altered brain structure? A systematic review and meta-analysis of morphometric neuroimaging in meditation practitioners. Neuroscience & Biobehavioral Reviews, no. 43, pp. 48-73, https://doi.org/10.1016/j.neubiorev.2014.03.016. Full text.

From the Abstract. Numerous studies have begun to address how the brain’s gray and white matter may be shaped by meditation. This research is yet to be integrated, however, and two fundamental questions remain: Is meditation associated with altered brain structure? If so, what is the magnitude of these differences?

To address these questions, we reviewed and meta-analyzed 123 brain morphology differences from 21 neuroimaging studies examining ∼300 meditation practitioners. Anatomical likelihood estimation meta-analysis found eight brain regions consistently altered in meditators, including areas key to meta-awareness (frontopolar cortex/BA 10), exteroceptive and interoceptive body awareness (sensory cortices and insula), memory consolidation and reconsolidation (hippocampus), self and emotion regulation (anterior and mid cingulate; orbitofrontal cortex), and intra- and interhemispheric communication (superior longitudinal fasciculus; corpus callosum). 

Publication bias and methodological limitations are strong concerns, however. Further research using rigorous methods is required to definitively link meditation practice to altered brain morphology.

For an update by the same authors, see “Alterations in the structure of the brain — review & implications.” 

Alterations in the structure of the brain — review & implications

Fox, Kieran C. R., & Rael B. Cahn. (2018). “Meditation and the brain in health and disease.” Forthcoming in The Oxford Handbook of Meditation, Farias, Brazier, & Lalljee, Eds. Full text.

The aim of this chapter is to provide an accessible introduction to the neuroscience of meditation. First, we review studies examining the relationship between meditation and alterations in the structure of the brain’s grey and white matter (so-called morphometric neuroimaging).

Next, we discuss findings from functional neuroimaging methods, such as functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) scans, and what they have taught us about the brain’s patterns of activity during different forms of meditation, how meditation alters the brain’s response to various tasks and experiences, and how the expertise of long-term meditators might be harnessed to help us explore subtle aspects of human cognition.

Third, we review electrophysiological methods of measuring brain activity during meditation, such as electroencephalography (EEG), and how these findings relate to what we have learned from morphometric and functional neuroimaging.

Finally, we discuss the implications of this research and of meditation more generally for brain health and psychological well-being. Specifically, we focus on how meditation might ameliorate the deficits related to cognitive aging, as well as help ameliorate the symptoms and underlying neural substrates associated with neurodegenerative and psychiatric disease.

The neurobiology of mindfulness (review)

Zeidan, F. (2014). The Neurobiology of Mindfulness Meditation. In The Handbook of Mindfulness. New York: Guilford Press. In press. Full text.

From the Introduction. For thousands of years, contemplatives have reported that enhancements in sensory awareness, cognition, and health can be accomplished through meditation practice. Before the development and utilization of neuroimaging and other scientific methodologies, the scientific world cast these descriptions as reflections of a relaxation response at best, and report biases associated with practitioner zeal at worst.

The recent surge in number of mindfulness-based studies has supported the claim that mindfulness meditation can improve a range of mental and physical health outcomes, and neuroimaging studies are beginning to identify the brain mechanisms that mediate the relationships between mindfulness meditation and such outcomes.

Although the neuroscientific investigation of mindfulness meditation is in its infancy, the premise of this chapter is that mindfulness meditation engages a unique, distributed network of brain regions. This chapter builds on previous neuroscientific work by offering a complementary perspective that focuses on a temporal account of the neurobiology of mindfulness, which considers the neurobiological basis of how mindfulness engages the brain over time. I first provide a brief overview describing some key neuroimaging methodologies used in research.

In the sections to follow, I provide a descriptive account of the neurobiological correlates of dispositional mindfulness, brief meditation training (1 week or less), the mindfulness based stress reduction (MBSR) program (approximately 8 weeks), and finally expert meditators (more than 1,000 hours of practice).

The subsequent section, concerning mindfulness and the default mode network, briefly describes how different levels of mindfulness-related experience affect task- independent neural processing. I then provide a longitudinal perspective of the brain structural correlates associated with different levels of mindfulness. Finally, I discuss considerations for future mindfulnessbased and other contemplative practice research.

Evidence from neuroimaging studies (lit review)

Marchand, W. R. (2014). Neural mechanisms of mindfulness and meditation: Evidence from neuroimaging studies. World Journal of Radiology, 6(7), 471-479. Full text.

mindimagesAbstract. Mindfulness is the dispassionate, moment-by-moment awareness of sensations, emotions and thoughts. Mindfulness-based interventions are being increasingly used for stress, psychological well being, coping with chronic illness as well as adjunctive treatments for psychiatric disorders. However, the neural mechanisms associated with mindfulness have not been well characterized. Recent functional and structural neuroimaging studies are beginning to provide insights into neural processes associated with the practice of mindfulness.

A review of this literature revealed compelling evidence that mindfulness impacts the function of the medial cortex and associated default mode network as well as insula and amygdala. Additionally, mindfulness practice appears to effect lateral frontal regions and basal ganglia, at least in some cases. Structural imaging studies are consistent with these findings and also indicate changes in the hippocampus. While many questions remain unanswered, the current literature provides evidence of brain regions and networks relevant for understanding neural processes associated with mindfulness.

Neurobiological and clinical features of mindfulness meditations

Chiesa, A., & Serretti, A. (2010). A systematic review of neurobiological and clinical features of mindfulness meditations. Psychological medicine, 40(08), 1239-1252. Full text.

From the Abstract. Mindfulness meditation (MM) practices constitute an important group of meditative practices that have received growing attention. The aim of the present paper was to systematically review current evidence on the neurobiological changes and clinical benefits related to MM practice in psychiatric disorders, in physical illnesses and in healthy subjects.

Electroencephalographic (EEG) studies have revealed a significant increase in alpha and theta activity during meditation. Neuroimaging studies showed that MM practice activates the prefrontal cortex (PFC) and the anterior cingulate cortex (ACC) and that long-term meditation practice is associated with an enhancement of cerebral areas related to attention.

From a clinical viewpoint, Mindfulness-Based Stress Reduction (MBSR) has shown efficacy for many psychiatric and physical conditions and also for healthy subjects, Mindfulness-Based Cognitive Therapy (MBCT) is mainly efficacious in reducing relapses of depression in patients with three or more episodes, Zen meditation significantly reduces blood pressure and Vipassana meditation shows efficacy in reducing alcohol and substance abuse in prisoners. However, given the low-quality designs of current studies it is difficult to establish whether clinical outcomes are due to specific or non-specific effects of MM.