Development of functional topography of the default mode subnetworks revealed by precision mapping.

The default mode network (DMN) is a functionally and anatomically heterogeneous network comprising distinct subsystems that support internally directed processes such as memory and self-related thought. The development of functional brain networks is critical for cognitive maturation, yet how DMN subnetworks develop remains unclear. Group-average approaches obscure individual variability and blur spatial details, limiting precise characterization of network topography. Using precision mapping in 547 participants aged 5-21 years, we delineated individualized DMN subnetworks and examined their development across multiple aspects, including functional segregation and spatial topography. We found that DMN subnetworks become increasingly functionally segregated from each other and from non-DMN networks with age, and exhibit greater topographic distinctiveness through boundary sharpening and reduced spatial overlap. Furthermore, the memory-related subnetwork showed a negative association between age and spatial extent, with a smaller surface area associated with better episodic memory performance. Our findings underscore the importance of characterizing multidimensional functional and topographical features at the individual level to better understand typical neurodevelopment and neurodevelopmental and psychiatric conditions.