Emergence of system roles in normative neurodevelopment

Significance The human brain is a complex system displaying intricate, dynamic functions. In a multidisciplinary effort, the recent application of tools from network science to characterize the interconnected nature of the brain has enabled a tremendous advance in our understanding of cognition. Here, we develop and apply an extension of these tools to define and characterize the role of cognitive systems in the larger scale brain network, and to map how these roles change during adolescent development, providing an important context for understanding psychopathology. Our results are also consistent with the hypothesis that individual variation in network configuration implies differential vulnerability to cognitive abilities or deficits. Adult human cognition is supported by systems of brain regions, or modules, that are functionally coherent at rest and collectively activated by distinct task requirements. However, an understanding of how the formation of these modules supports evolving cognitive capabilities has not been delineated. Here, we quantify the formation of network modules in a sample of 780 youth (aged 8–22 y) who were studied as part of the Philadelphia Neurodevelopmental Cohort. We demonstrate that the brain’s functional network organization changes in youth through a process of modular evolution that is governed by the specific cognitive roles of each system, as defined by the balance of within- vs. between-module connectivity. Moreover, individual variability in these roles is correlated with cognitive performance. Collectively, these results suggest that dynamic maturation of network modules in youth may be a critical driver for the development of cognition.