Understanding the development of a functional brain circuit: reward processing as an illustration.

Aberrant reward processing is common in psychiatric disorders that begin during development. However, our understanding of the early reward system is limited, due to few studies assessing reward engagement across development. Moreover, the interpretation of these findings is based primarily on our understanding of the adult reward system. Here, we argue that approaches to early reward processing must be re-framed within the context of developmental transitions. This alternate perspective takes into account unique, age-specific brain network functions that promote adaptive behaviors as environmental demands change from infancy through childhood. We survey the literature on developing reward systems and ask the following critical questions: (1) how are rewarding stimuli defined for infants and children? (2) do adult-defined neural reward circuits also support early reward behavior? and (3) how can early circuit perturbation impact infant and adult circuit function? Altogether, we argue that this developmental niche-centered framework is needed for conceptually and theoretically approaching developmental research questions, including but also extending beyond the scope of reward. Finally, this framework can help us understand how disturbance in developmental processes may ultimately manifest as pathology.