Benchmarking functional brain network organization in childhood and its similarity to adults.

Understanding how large-scale functional networks mature across development is essential for linking brain organization to cognition and behavior. Thus, the population-level organization of functional networks in children and how it compares to adult network architecture deserves further study. Using resting-state fMRI data from 7,316 children aged 9-10 years in the Adolescent Brain Cognitive Development (ABCD) Study, we mapped functional networks in matched discovery (n = 3,624) and replication (n = 3,692) cohorts in the cerebral cortex, basal ganglia, thalamus, and cerebellum. Functional connectivity and network topography were highly reproducible across child cohorts, demonstrating that large-scale network organization can be reliably estimated in childhood at the population scale. Comparisons with the adult Human Connectome Project (HCP; n = 1,000) dataset revealed reduced cross-age similarity compared to the within-age similarity. Our findings indicate that by late childhood, the global scaffold of brain networks approximates adult architecture with continued refinement, particularly in higher-order association systems. This large-scale, discovery-replication framework establishes a reproducible benchmark for cross-age functional network mapping, providing a foundation for longitudinal analyses of maturation across adolescence.