PROJECT SUMMARY/ABSTRACT Adolescence is a period of considerable neural development marked by cognitive and behavioral changes including increased engagement in novelty-seeking and risk-taking behaviors (e.g., substance use experimentation). Approximately 8% of youth in the United States report having used alcohol by the end of 6th grade. Early substance use initiation is linked to increased risk of substance use and other psychiatric disorders as well as greater psychosocial difficulties by adulthood. According to the imbalance model of adolescent neural development, increased risk-taking is due to different developmental patterns between frontal and striatal regions of the brain. This imbalance results in a weaker inhibitory control system coupled with a more mature striatal reward-processing system during adolescence. Altered patterns of functional neural connectivity between frontal and striatal regions have been observed prior to substance use initiation, and may serve as a predisposing vulnerability factor for development of substance use disorder. However, this potential marker has yet to be examined prospectively, prior to adolescence, in youth who endorse early but minimal exposure to alcohol (sipping). The goal of the proposed study is to examine reward-related fcMRI prospectively as a predictor of future substance use in youth aged 9-10 years old who endorse early but minimal exposure to alcohol (i.e., sipping). To examine this question, data gathered from approximately 11,500 youth as part of the ABCD consortium will be used. Alcohol and substance use and reward-related functional connectivity will be examined at baseline (youth ages 9-10 years old) and 2 years later (11-12 years old). Ultimately, the knowledge gained from this project can be used to inform public health policies to promote prevention and early intervention.