Explaining Brain–Behavior Relations: Inhibitory Control as an Intermediate Phenotype Between the N2 ERP and the Externalizing Spectrum in Childhood

Identifying neural and cognitive mechanisms in externalizing problems in childhood is important for earlier and more targeted intervention. Meta-analytic findings have shown that smaller N2 event-related potential (ERP) amplitudes, thought to reflect inhibitory control, are associated with externalizing problems in children. However, it is unclear how (i.e., through which cognitive processes) N2 amplitudes relate to externalizing problems. We examined whether inhibitory control may be a cognitive process that links N2 amplitudes and externalizing problems in early childhood. Children (N = 147, 74 girls) were assessed at four time points, spanning 3–7 years of age. Children’s externalizing behavior was assessed via questionnaires completed by mothers, fathers, and teachers/secondary caregivers. Children’s inhibitory control was assessed using twelve performance-based tasks and two questionnaires. Developmental scaling linked differing measures of inhibitory control and externalizing behavior across ages onto the same scale. Children’s N2 amplitudes were extracted from electroencephalography data collected during a go/no-go task. Smaller N2 amplitudes were associated with externalizing problems and poorer inhibitory control. A concurrent analysis of indirect effects revealed that poorer inhibitory control partially explained the association between smaller N2 amplitudes and externalizing problems, even when controlling for the child’s age, sex, and socioeconomic status. This is among the first studies to link N2 amplitudes, inhibitory control, and externalizing problems during early childhood. Findings suggest that smaller N2 amplitudes may be an early neural indicator of inhibitory control deficits and externalizing psychopathology. Moreover, inhibitory control may be an important target for early intervention in the development of externalizing psychopathology.