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Intrinsic timescale is a commonly used measure of spontaneous neural dynamics that quantifies the temporal window of processing in neuronal populations. It displays a hierarchical cortical organization across species and imaging modalities, with shorter timescales in sensorimotor cortex and longer timescales in association cortex. However, less is known about how intrinsic timescale evolves during human brain development. Here, we estimate intrinsic timescale in two independent youth datasets and examine its developmental patterns. We find that changes in intrinsic timescale follow a hierarchical gradient along the sensorimotor-to-association (S–A) axis. Analysis of an independent adult dataset suggests this pattern stabilizes in adulthood. Together, these findings highlight intrinsic timescale as a marker of hierarchical brain maturation during development.

We show that white matter tracts are differentially positioned in the cortical hierarchy to support specific cognitive functions, and that tracts spanning the hierarchy connect regions with greater cognitive diversity. Moreover, tracts situated within the same hierarchical level connect biologically similar regions, while those crossing the hierarchy bridge distinct biological milieux to support diverse cognitive functions. The placement of tracts in the cortical hierarchy also reflects developmental variation in tract microstructure and individual differences in cognition.