Cellular and molecular underpinnings of functional networks in the human brain.

Understanding how cellular and molecular architecture underpins the large-scale organization of human brain function is a central challenge in neuroscience. By integrating transcriptomic (microarray data and single-nucleus RNA-sequencing [sn-RNA] data), molecular imaging, and neuroimaging datasets, we observed spatial correspondences suggesting that the distributions of diverse cell types, neurotransmitter systems, and mitochondrial phenotypes are aligned with intrinsic connectivity networks (ICNs)-the macroscale scaffolding of brain function. These associations extend beyond local correspondence to reflect network-level structure: inter-ICN similarity networks derived from cellular and molecular profiles significantly recapitulate both static and dynamic patterns of functional network connectivity (FNC), mirroring the established division of ICNs into canonical functional domains. Importantly, these cellular and molecular profiles not only colocalize with ICNs and FNCs but also appear to support their role as intermediaries linking microscale biological substrates to cognitive function. Mediation analyses reveal that specific ICNs statistically mediate the relationship between microscale cell-type architecture and domain-specific cognitive and behavioral processes. Moreover, FNCs capture the mediating pathways linking cell-type and neurotransmitter similarity networks to cognitive network organization. Taken together, our findings suggest that the brain's functional architecture shows systematic associations with cellular and molecular organization, which may act as a biological constraint guiding functional network formation and contribute to the neural basis of cognition.