The Diversity and Multiplexity of Edge Communities within and between Brain Systems

Abstract

The human brain is composed of regions that can be grouped into functionally specialized systems. These systems transiently couple and decouple across time to support complex cognitive processes. Recently, we proposed an edge-centric model of brain networks whose elements can be clustered to reveal communities of connections whose co-fluctuations are correlated across time. It remains unclear, however, how these co-fluctuation patterns relate to traditionally-defined brain systems. Here, we address this question using data from the Midnight Scan Club. We show that communities transcend traditional definitions of brain systems, forming a multiplexed network in which all pairs of brain systems are linked to one another by at least two distinct communities. Mapping communities back to individual brain regions and deriving a novel distance metric to describe the similarity of regions' edge community profiles'', we then demonstrate that the within-system similarity of profiles is heterogeneous across systems. Specifically, we find that heteromodal association areas exhibit significantly greater diversity of communities than primary sensory systems. Next, we cluster the entire cerebral cortex according to the similarity of regions' community profiles, revealing systematic differences between traditionally-defined systems and the detected clusters. Specifically, we find that regions in heteromodal systems exhibit dissimilar community profiles and are more likely to form their own clusters. Finally, we show show that communities are highly personalized and can be used to identify individual subjects. Collectively, our work reveals the pervasive overlap of communities across the cerebral cortex and characterizes their relationship with the brain's system level architecture. Our work provides clear pathways for future research using edge-centric brain networks to investigate individual differences in behavior, development, and disease.