neuro, graded (ep.2) | 6 key brain areas associated with meditation (Fox et al., 2014)
the study
Fox et al. (2014) pooled 21 Magnetic Resonance Imaging (MRI) studies including a total of 300 experienced meditators. They examined structural differences e.g. volume, thickness and density of meditator versus non-meditator brains.
what they found
Six brain regions were enlarged in meditators. These regions were consistent across different studies and analysis methods:
Insula - processes internal body sensation (heartbeat, breath). A plausible link to meditation’s attention-to-breath practices.
Anterior/mid-cingulate cortex (ACC/MCC) - tied to self-regulation and shifting from automatic reaction to conscious control of cognition and emotions. The most frequently reported region in the review.
Frontopolar cortex (BA10) - linked to introspection and metacognition (ability to think about your own thoughts). Showed up across very different meditation traditions, suggesting it may generalise rather than being style-specific.
Hippocampus - involved in memory and emotional learning. Also a region that’s used during mind-wandering.
Somatomotor cortices - process touch, pain, and body position and are found alongside insula changes in the same body-aware practitioners.
Inferior temporal gyrus - a puzzling finding, as this brain region is tied to enhanced visual processing; the authors reason that some meditation styles are practised eyes-open with sustained attention, hence why visual processing may happen, although this is speculative.
Other brain regions implicated, although less consistently across studies:
Precuneus - involved in body image, self-related processing, and shifting attention. However, fewer studies actually measured this region directly.
Orbitofrontal cortex (OFC) - connected to the emotional brain (amygdala, striatum) but also involved in flexible, “in the moment” evaluation of what matters right now, as opposed to relying on fixed past associations. Also implicated in down-regulating negative emotion. Plausible fit with meditation’s benefits for depression, anxiety, and stress; again, correlational, not demonstrated as causal.
White matter pathways
(i) Corpus callosum - connectivity between two hemispheres - the wiring that connects the various prefrontal grey-matter changes (BA10, insula, OFC, ACC) across the left and right sides of the brain, i.e., a byproduct of those other findings, not a separate effect.
(ii) Superior Longitudinal Fasciculus (SLF) - connects parietal (body-awareness) regions to prefrontal (executive) regions, within one hemisphere, not across the two. Increased connectivity between “sensing the body” regions and “regulating behaviour” regions.
is having a bigger brain region actually better?
Not necessarily.
It’s natural to think “bigger region = more developed/better,” since regions do grow with learning and shrink with decline. However, healthy brain development also happens through pruning (removing connections), not just growth. So growth isn’t inherently the “good” direction. Further, some regions are enlarged in disorders like Obsessive Compulsive Disorder (OCD), so structural increase, on its own, doesn’t signal benefit.
what is missing?
A link between whether the structural difference actually correlates with something meaningful, e.g. better mood, less anxiety, sharper attention, etc. The connection to real-world function/wellbeing hasn’t actually been tested/shown yet.
the magnitude of effect
Effect size demonstrates the magnitude of difference between meditators and non-meditators (0 being no effect, > 1 a large effect).
A moderate, d ≈ 0.44–0.46 effect was reported overall and is a comparable effect size to well-established behavioural and therapeutic interventions generally, not a small or trivial number.
a key question is: does meditation cause this?
still unclear, for three reasons:
Almost all of this data is cross-sectional, a snapshot in time, comparing meditators to non-meditators. Therefore, one cannot rule out the possibility that experienced meditators who have already enlarged brain regions may be drawn to meditate, rather than the meditation caused these changes. A longitudinal study that tracks the same people over time would provide more causal evidence.
Some studies show short bursts of meditation training in non-meditators (novices) show similar regional patterns to long-term meditation practitioners, a point in favour of causation, though not proof.
Counterintuitively, more meditation experience didn’t predict bigger effects. If meditation itself were driving the change, you would expect more practice to result in more change. The authors reason that age-related brain shrinkage in long-term (typically older) practitioners is muddying the result, but with only 15 studies in that analysis, they’re honest that it’s too unstable to conclude from.
evidence grade: emerging.
(!) nearly all the largest effect sizes came from the smallest studies (under 40 people), this is a sign of publication bias.
although, the associations are fairly reliable across methods, which is a real strength.
but the authors themselves are explicit that causation isn’t confirmed.
the defensible claim is: meditation is associated with structural differences in specific brain regions, of a similar magnitude to other well-established interventions; further and stronger research is needed to show “meditation causes these brain changes.”
Hope you enjoyed this article.
Sophia
References
Fox, K. C. R., Nijeboer, S., Dixon, M. L., Floman, J. L., Ellamil, M., Rumak, S. P., Sedlmeier, P., & Christoff, K. (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. https://doi.org/10.1016/j.neubiorev.2014.03.016
