ABSTRACT
Recent work has uncovered relationships between evolutionarily new small and shallow cerebral indentations, or sulci, and human behavior. Yet, this relationship remains unexplored in the lateral parietal cortex (LPC) and the lateral parieto-occipital junction (LPOJ). After defining thousands of sulci in a young adult cohort, we revised the previous LPC/LPOJ sulcal landscape to include four previously overlooked, small, shallow, and variable sulci. One of these sulci (ventral supralateral occipital sulcus, slocs-v) is present in nearly every hemisphere and is morphologically, architecturally, and functionally dissociable from neighboring sulci. A data-driven, model-based approach, relating sulcal depth to behavior further revealed that the morphology of only a subset of LPC/LPOJ sulci, including the slocs-v, is related to performance on a spatial orientation task. Our findings build on classic neuroanatomical theories and identify new neuroanatomical targets for future "precision imaging" studies exploring the relationship among brain structure, brain function, and cognitive abilities in individual participants.
ABSTRACT
A salient neuroanatomical feature of the human brain is its pronounced cortical folding, and there is mounting evidence that sulcal morphology is relevant to functional brain architecture and cognition. Recent studies have emphasized putative tertiary sulci (pTS): small, shallow, late-developing, and evolutionarily new sulci that have been posited to serve as functional landmarks in association cortices. A fruitful approach to characterizing brain architecture has been to delineate regions based on transitions in fMRI-based functional connectivity profiles; however, exact regional boundaries can change depending on the data used to generate the parcellation. As sulci are fixed neuroanatomical structures, here, we propose to anchor functional connectivity to individual-level sulcal anatomy. We characterized fine-grained patterns of functional connectivity across 42 sulci in lateral prefrontal (LPFC) and lateral parietal cortices (LPC) in a pediatric sample (N = 43; 20 female; ages 7-18). Further, we test for relationships between pTS morphology and functional network architecture, focusing on depth as a defining characteristic of these shallow sulci, and one that has been linked to variability in cognition. We find that 1) individual sulci have distinct patterns of connectivity, but nonetheless cluster together into groups with similar patterns - in some cases with distant rather than neighboring sulci, 2) there is moderate agreement in cluster assignments at the group and individual levels, underscoring the need for individual-level analyses, and 3) across individuals, greater depth was associated with higher network centrality for several pTS. These results highlight the importance of considering individual sulcal morphology for understanding functional brain organization. Significance Statement: A salient, and functionally relevant, feature of the human brain is its pronounced cortical folding. However, the links between sulcal anatomy and brain function are still poorly understood - particularly for small, shallow, individually variable sulci in association cortices. Here, we explore functional connectivity among individually defined sulci in lateral prefrontal and parietal regions. We find that individual sulci have distinct patterns of connectivity but nonetheless cluster together into groups with similar connectivity - in some cases spanning lateral prefrontal and parietal sulci. We further show that the network centrality of specific sulci is positively associated with their depth, thereby helping to bridge the gap between individual differences in brain anatomy and functional networks leveraging the sulcal anatomy of the individual.
