Human visual cortex as a window into the developing brain by Kalanit Grill-Spector

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A central question in neuroscience is how does brain structure and function develop and enable sophisticated behaviors such as recognizing faces and words. Using human visual cortex as a model system, we examine how the gray and white matter microstructure develops during early infancy and childhood and how these developments relate to development of function and behavior. Here we will present exciting new results from both cross-sectional and longitudinal multimodal studies using functional MRI (fMRI), quantitative MRI (qMRI), diffusion MRI (dMRI) and behavior.

Longitudinal measurements in infants (0-6 months) reveal profound and non-uniform myelination in both the white and gray matter, which we validated with transcriptomics. In white matter fascicles, myelination is linked with both spatial gradients and myelin content at birth. In visual cortex, microstructure proliferates progressively more rapidly across areas of visual processing hierarchies.

Interestingly, high-level regions of ventral temporal cortex (VTC) involved in visual recognition show protracted development that continues throughout childhood and adolescence. Cortical myelination in face and word-selective regions continues from childhood to adulthood, which we validated with myelo-histology. Examination of the relationship between white matter connections, cytoarchitectonics, and brain function reveals that white matter connections of VTC are linked to cytoarchitecture rather than category-selectivity in childhood, but to both cytoarchitecture and category-selectivity in adulthood. This suggests that cytoarchitecture may scaffold white matter connections early in development, and visual experience may enhance the development of category-specific connections. Finally, longitudinal examination of functional selectivity in children over 5 years shows that face- and word-selective regions expand and become more category-selective, but limb-selective regions surprisingly shrink and lose their preference for limbs. Distributed VTC responses show corresponding developments, which not only affect category information in distributed VTC responses, but also predict improvements in face and word recognition abilities across childhood development.

Together these data not only show a striking interplay between microstructural, functional and behavioral development which do not follow a uniform trajectory, but also reveal the important role of myelination in brain development.