Effects of working memory and reward reactivity on externalizing behaviors in the ABCD study

Deficits in working memory and reward reactivity may contribute to behavioral dysregulation. Using behavioral and neural data from the Adolescent Brain and Cognitive Development (ABCD 5.1) study, we examined associations among biological systems, environmental risk, and childhood externalizing behaviors (i.e., aggression, rule breaking). Behavioral measures included List Sorting and Cash Choice tasks to assess working memory and reward processing, respectively. Neural measures included the functional magnetic resonance imaging (fMRI) emotional n-back (EN-back) and Monetary Incentive Delay (MID) tasks to assess working memory (2-back vs. 0-back) and reward processing (anticipation: reward vs. neutral; feedback: reward success vs. failure), respectively. We conducted linear mixed effects models with discovery and replication samples to investigate correlates of externalizing behaviors at baseline (behavioral: n = 7448; neural: n = 3265) and two years later (behavioral: n = 7127; neural: n = 3151). We also tested whether these relationships differed by sex, adjusting for age, socioeconomic status, and stressful life events. Lower behavioral working memory was related to concurrent externalizing behaviors. Baseline stressful life events was the strongest predictor of externalizing behaviors two years later, highlighting environmental adversity's role in development of externalizing behavior. Reward reactivity (behavioral or reward anticipation and feedback neural activation) and working memory neural activation were not associated with externalizing behaviors at either time point. Findings suggest that environmental stress and behavioral working memory explain variability in externalizing behaviors within the scope of the measures examined here. These findings highlight the need for continued research clarifying the neural mechanisms underlying externalizing behavior.