The default mode network is a group of brain regions that are more active at rest than during focused outside tasks. A 2001 paper proposed that they reflect a default state of the resting brain rather than noise (Raichle et al., 2001). A 2019 review links the network to remembering, imagining the future and social thinking (Buckner and DiNicola, 2019).
Psychedelic research made the term famous. In a 2012 London study of intravenous psilocybin, scans showed decreases in hub regions, and weaker coupling between two default-mode hubs (Carhart-Harris et al., 2012). That fed a popular slogan that psychedelics shut the network down.
Later work is more modest. The one detailed fMRI study of DMT, in 20 volunteers in 2023, found the network became more connected with the rest of the brain while the boundaries between networks blurred (Timmermann et al., 2023). fMRI tracks blood oxygen, not neurons directly, and the studies are small. How these changes relate to the experience, or to any lasting effect, is unresolved.
Sources
- Raichle et al., 2001, PNAS: a default mode of brain function
- Buckner and DiNicola, 2019, Nature Reviews Neuroscience: the default network
- Carhart-Harris et al., 2012, PNAS: psilocybin fMRI
- Timmermann et al., 2023, PNAS: DMT EEG-fMRI
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