PROJECT SUMMARY/ABSTRACT The hippocampus is composed of cytoarchitecturally-distinct subfields that support specific memory and learning functions. Evidence suggests distinct developmental trajectories in hippocampal subfields throughout childhood and adolescence, periods in which environmental factors exact strong influence on brain development. However, evidence is largely from cross-sectional samples, is based on inconsistent practices for delineations of subfields, and is limited by the power and diversity within single studies. Thus, developmental trajectories of hippocampal subfields remain unclear, prohibiting the systematic study of the influence of environmental factors on hippocampal development. Variations in total hippocampal volume across development have been linked to socioeconomic status, a proxy for access to material resources, medical care, and quality education in one’s environment. Low household socioeconomic status in childhood is associated with worse cognitive abilities later in adulthood, and low neighborhood socioeconomic status (an additional index of social capital and connectedness) further predicts poor behavioral outcomes beyond the household, especially in adolescence. The proposed study examines differential vulnerability of hippocampal subfield structures to variations in household and neighborhood socioeconomic across development. Understanding of normative developmental changes in subfield structure and vulnerability to low socioeconomic environments can have significant implications for individual and community interventions. However, testing these questions requires a large sample size, adequate coverage of age, specialized ultra-high-resolution scans, and sufficient representation of the diverse United States population. The proposed study will achieve this using integrative data analysis, an advanced latent modeling approach that directly addresses differences in methodologies while allowing new hypotheses to be tested in existing data. Hypotheses will be tested using a novel integrated longitudinal dataset of 678 typically developing subjects covering the span of 4- to- 25-years from four geographically- and demographically-diverse sites across the United States by pursuing these specific aims: Aim 1) Characterize typical developmental trajectories of hippocampal subfields in a diverse multi-site study pediatric sample; and Aim 2) Elucidate the link between variations in socioeconomic status and the development of hippocampal subfields. The hippocampus is implicated in neurodevelopmental disorders such as depression, schizophrenia, and low SES also confers risk for neurodevelopmental disorders. Thus, obtaining accurate characterization of hippocampal subfield development trajectories and identifying the effects of household and neighborhood SES in a large sample will pave the way for early identification of neurodevelopmental disorders and targeted intervention for specific factors associated with socioeco...