4. Precision mapping of functional brain networks in individuals with depression

COEX 

Precision functional mapping is the emerging practice of delineating functional brain areas or networks and studying brain-behavior relationships within individuals, as opposed to at the group-level, typically using a large amount of fMRI data per-subject acquired longitudinally. Here, we applied precision functional mapping in individuals with major depression who were studied for up to 1.5 years, and found that the salience network is expanded nearly 2-fold due to borders of the network shifting outwards and encroaching upon neighboring functional systems. Cortical expansion of the salience network was trait-like – stable over time, unaffected by mood state, and detectable in a separate sample of children scanned before the onset of depression symptoms later in adolescence. In contrast, functional connectivity between different pairs of frontostriatal salience network nodes was state-dependent and closely tracked fluctuations in distinct symptoms (anhedonia, anxiety) over time within and across individuals. Together, these findings reveal new patterns of functional network topography and connectivity that are neural traits and states, respectively, characteristic of depression, and highlight the utility of deeper characterizations of functional neuroanatomy and behavior within individuals as an alternative to studying population-level central tendencies.