Differences in the trajectory of P300 amplitude development related to familial externalizing may provide important clues to developmental processes in the etiology of disinhibited behavior disorders. Given that the intercept and slope of P300 growth trajectories in adolescence and early adulthood are significantly influenced by a common set of genes, these trajectories may provide clues about how genetic influences on individual differences in the development of the central nervous system lead to vulnerability for a disorder. For example, past research involving functional MRI (Rangaswamy et al., 2004) and current source localization (Chen et al., 2007) has suggested a link between P300 amplitude reduction related to alcoholism risk and frontal cortex abnormalities, including areas involved in working memory systems (McCarthy, Luby, Gore, & Goldman-Rakic, 1997). The genetic risk indexed by P300 amplitude development may be mediated by developmental differences in such brain systems.
