Default mode network connectivity and temperament are associated with internalizing symptoms in early childhood

This study investigates neural and temperament precursors to internalizing psychopathology. Increased default mode network (DMN) functional connectivity and decreased frontoparietal network (FPN) connectivity are established neural signatures of internalizing disorders in adults, but it is unknown if these patterns represent early-emerging vulnerability. In a community sample of typically developing children aged 4-6 years, we examined the concurrent associations of resting-state functional connectivity and temperament with internalizing symptoms. Of the 78 children retained following fNIRS quality control, 66 were included in the analytic sample (age range = 48-83 months; 38 female, 28 male; 78% White; predominantly high SES), We hypothesized that increased DMN connectivity, decreased FPN connectivity, and temperament traits of high negative affect and low surgency would be associated with higher internalizing problems. Functional connectivity was measured using functional near-infrared spectroscopy (fNIRS), a child-friendly neuroimaging technique. Internalizing symptoms and temperament were assessed via parent report using the Child Behavior Checklist and Child Behavior Questionnaire. A multiple linear regression revealed that greater DMN connectivity, higher negative affect, and lower surgency were significantly and independently associated with internalizing symptoms. FPN connectivity was not significantly associated with internalizing symptoms. These findings suggest that a key neural signature of adult depression-DMN hyperconnectivity-is associated with subclinical symptoms in early childhood, supporting its role as a primary vulnerability marker. The absence of an FPN association may reflect the protracted maturation of this cognitive control network, though longitudinal data are required to test whether neural risk factors for internalizing disorders emerge on distinct developmental timetables.