Scientists have discovered that the salience network, a set of brain regions that decides what you focus on and how rewarding something feels, is much larger in people who experience major depression. Using an intensive form of brain-scan analysis called precision functional mapping, the research team repeatedly scanned the same volunteers over many sessions. They found that, on average, the salience network covered almost twice as much brain surface in depressed participants as in people with no psychiatric history.
This difference was stable: the network stayed the same size regardless of whether symptoms were mild or severe, and it did not shrink after standard brain-stimulation treatment. In children who later developed depression, the network was already enlarged before any mood problems appeared, hinting that the change could be an early risk marker rather than a consequence of low mood.
The enlarged network seems to spread into neighbouring areas involved in self-reflection and complex thinking, potentially disturbing how the brain balances emotion, motivation and higher-order thought. Although scanning every patient this intensively is not practical today, the finding may help clinicians refine future brain-stimulation therapies by targeting the precise areas that drive particular symptoms.
Nature: “Frontostriatal salience network expansion in individuals in depression.”
Dense, longitudinal fMRI in six deeply scanned patients and several larger replication samples showed that the cortical representation of the salience network is roughly doubled in most people with major depression. The expansion is driven mainly by shifts along network borders, remains constant over time, and can be detected in at-risk adolescents, suggesting it is a trait-level vulnerability marker rather than a state marker.
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