Functional gradient of the fusiform gyrus and its underlying molecular basis

Evidence has evinced the functional complexity, anatomical heterogeneity, connectivity diversity, and clinical relevance of the fusiform gyrus. We aimed to investigate the hierarchical organization of the fusiform gyrus and its underlying molecular basis. Resting-state functional MRI data of 793 healthy subjects were collected from a discovery dataset and two independent cross-scanner, cross-race validation datasets. Functional gradients of the fusiform gyrus were calculated based on the voxel-wise fusiform gyrus-to-cerebrum functional connectivity to reflect its functional organization. Transcription-neuroimaging spatial correlation analysis was performed to determine genes with expression levels tracking the fusiform gyrus functional gradient. The dominant functional gradient that explained the greatest connectivity variance showed an anterior-posterior axis across the fusiform gyrus. More important, there was a strong association between the fusiform gyrus-dominant gradient and gene expression profiles, with two gene sets contributing significantly to this association yet differing in their specific expression and functional annotation. In addition, the fusiform gyrus-dominant gradient was linked closely to intrinsic geometry, slightly to cortical morphology, and gradually to behavioral domains from high-level cognitive processes to low-level sensory functions. Our findings add to the extant knowledge regarding the topographic organization of the fusiform gyrus by informing a novel conceptualization of how functional heterogeneity and multiplicity co-occur within the fusiform gyrus.