Default Mode Network, Amygdala and Other Brain Claims Checked

Two brain terms appear again and again in meditation articles: the "default mode network" and the "amygdala". This page checks the most common claims against the studies behind them. It is information only. For the wider picture, start with meditation and the brain.

What the terms mean

The default mode network is a set of brain regions that tends to be active when the mind wanders and thinks about the self. Researchers link it with mind-wandering and self-referential processing. [1] The amygdala is a small brain structure that helps coordinate stress responses. [2] Calling either "the stress brain" or "the worry brain" is a simplification of more complicated brain activity.

Claim 1: "Meditation switches off the default mode network"

What was studied. A study compared experienced meditators with matched meditation-naive controls while they did concentration, loving-kindness and choiceless awareness meditation. [1] The main default mode regions (medial prefrontal and posterior cingulate cortices) were relatively deactivated in the experienced meditators across all three styles. [1] They also showed stronger coupling between regions linked to self-monitoring and cognitive control. [1] The authors said this was consistent with decreased mind-wandering. [1]

Limits. The groups were defined by experience, not randomly assigned, so people who stick with meditation may simply differ. The word "relatively" matters: the network was less active, not off. And the study does not show that quieter scans mean better health.

A separate fMRI study of 14 practitioners doing breath-focused meditation found default mode activity during periods of mind-wandering, salience network activity when they noticed it, and executive network activity as they refocused. [3] So the network is part of a normal cycle of drifting and returning, not something meditation permanently shuts down. [3]

Claim 2: "Meditation shrinks the amygdala"

What was studied. In an early MRI study, 26 stressed but healthy people took an 8-week MBSR course. Reductions in perceived stress correlated with decreases in right basolateral amygdala gray matter density. [4] The abstract describes one group and does not mention a control group, and it reports a correlation between stress change and tissue change, not proof that the course caused it. [4]

Later evidence. A randomized trial of 35 stressed, unemployed adults compared 3 days of mindfulness training with a matched relaxation program. The mindfulness group showed lower connectivity between the right amygdala and a frontal region (the subgenual anterior cingulate) at rest. [2] The authors called this an initial indication, and the sample was small. [2] A systematic review also reported lower amygdala activity and stronger links to the prefrontal cortex after MBSR. [5]

But a much larger pair of randomized trials (218 people) found no structural brain changes after MBSR compared with a waitlist or a matched active control, including in regions drawn from earlier MBSR studies. [6] So changes in how the amygdala works (function) have somewhat more support than changes in its size (structure), and neither is settled.

Claim 3: "Meditation rewires the brain"

"Rewiring" is a marketing phrase, not a measurement. A review in Nature Reviews Neuroscience said the neural mechanisms behind mindfulness benefits remain unclear and that more rigorous studies are needed. [7]

Summary table

How to read the next headline

Ask four questions: Was there a comparison group? Was it randomized? How many people? Did a symptom or only a scan change? See quality and bias in meditation research and does meditation work?. For attention and mind-wandering during practice, see mind wandering and attention.