Individualized network topography in pre-adolescent children and adults using naturalistic precision fMRI

Group-averaged network definitions, commonly used in developmental functional connectivity research, limit our understanding of how network topography may change with age and can lead to inaccurate estimates of age effects on intra- and inter-network functional connectivity. Here, we collected a precision fMRI dataset from 24 parent-child pairs (children 6 to 8 years, 13 females; adults 33 to 47 years, 12 females) during passive video viewing and derived individual template-matched functional network maps from 60 minutes of motion-censored data per participant. Overall, large-scale network architecture was broadly shared between children and adults, with no age-effects observed for network-level surface area, few age differences in network boundaries and generally lower assignment confidence in children. Considering inter-individual similarity in network topography, association networks showed stronger within-family similarity and no overall effect of age on similarity of networks between pairs of individuals. We further asked how individualized network definitions might impact estimates of age effects on dense functional connectivity. While all approaches pointed to greater within-network functional connectivity in adults, we found that individualized approaches had larger age effects and lower sensitivity to head motion. Together, our results suggest that, relative to adults, pre-adolescent children show reduced network assignment confidence and weaker within-network connectivity, but limited differences in network borders and size, and underscore the value of individualized mapping for improving topographic reliability and increasing sensitivity to age effects. Significance statement Brain network organization varies between individuals, yet most research on age effects on functional connectivity relies on adult-derived group templates, potentially misrepresenting pediatric brain organization and hindering interpretations of age differences in network topography and functional connectivity. Here, we used naturalistic precision fMRI to define functional networks in individuals and compared topography and connectivity between adults and pre-adolescent children. We found limited age effects on network topography and that children had lower confidence in their network assignments. Importantly, we found that defining networks in individuals improved sensitivity to age effects on functional connectivity and reduced dependence on head motion. These findings highlight the potential for person-specific network definitions for improving sensitivity and specificity of findings in pediatric functional connectivity research.