To our knowledge, this is the first study to use a polygenic approach to isolate brain circuits related to externalizing. We found that an aggregate measure of genetic risk for externalizing was associated with functional connectivity in a circuit centered on left amygdala that included several cortical (bilateral IFG pars triangularis, left rostral ACC) and subcortical (bilateral amygdala, hippocampus, striatum) regions. These regions are central to psychological processes previously implicated in externalizing, including emotion regulation (amygdala, ACC), impulse control (IFG), and reward learning (caudate, putamen) (Baskin-Sommers et al., 2012; DeVito et al., 2013; Glenn and Yang, 2012; Sadeh et al., 2015). Although connectivity studies on the latent externalizing spectrum are sparse, there is evidence from within-region activation studies of increased amygdala reactivity and heightened engagement of executive control regions in impulsive and externalizing individuals (Foell et al., 2016; Sadeh et al., 2013). Our findings extend this work by showing that externalizing is also associated with increased amygdala connectivity at rest, primarily to PFC (see Figure 1). These findings also converge with neuroimaging studies conducted with specific externalizing disorders, which tend
