Individualized Subcortical Functional Brain Organization Is Related to Diagnosis, Symptoms, and Behavior in Major Depressive Disorder.

BACKGROUND

Individualized brain systems mapping is a recently developed method for understanding person-specific functional brain organization using human functional magnetic resonance imaging data. Abnormal structure and function in the subcortex have previously been implicated in individuals with major depressive disorder (MDD). However, the systems-level functional organization of the subcortex in MDD has yet to be investigated. Moreover, almost all prior studies of brain systems in MDD have used group-level functional brain mapping that assumes organizational homogeneity across individuals.

METHODS

In this study, the functional systems organization of the subcortex was mapped in individuals with MDD (n = 288, 67% female) and healthy control participants (n = 40, 63% female). Individualized subcortical system metrics were then related to psychiatric diagnosis and symptoms and related behavioral measures. We evaluated hypothesis-driven comparisons in the size of subcortical systems' representation of the control, default, affective, and salience systems.

RESULTS

Results include significant differences between participants with depression and healthy participants in subcortical control system representation (z = 2.77, p = .006, d = 0.46). Specifically, in the MDD group, the control system was more represented in the thalamus (z = 2.99, p = .003, d = 0.51). Total subcortical control system representation was associated with behavioral indices of cognitive control (i.e., A-not-B total correct response; r = 0.13, p = .029).

CONCLUSIONS

Taken together, these findings provide the first evidence that mental illness is related to individualized subcortical system representation and thus provide new insight for neural models of MDD and related neuropsychiatric conditions.