Developmental changes in connectivity-based parcellation in typical cortical areas during early life.

The human brain undergoes profound developmental changes in the cortex during early life. Functional parcellation of the cortex may also be altered, but there was a limited methodology for quantification. Here, we employed connectivity-based parcellation of sub-regions as a marker to characterize the heterogeneous development of the cerebral cortex. Particularly, we investigated the parcellation of primary motor (M1), sensory cortex (S1), and insula based on tractography-based connectivity among 3 stages during first 2 yr of life and also adulthood. We identified 4 and 3 sub-regions along superior-to-inferior axis in M1 and S1, respectively, and 2 sub-regions along anterior-to-posterior axis in insula. Connectivity profiles and volume fractions of different sub-regions showed distinct development changes. Specifically, measures of each sub-region in M1 and S1 showed a steady development during first 2 yr of life and gradually became similar to adulthood patterns. In contrast, sub-regions in insula exhibited nearly no change in this stage but tremendous differences in adult group. These findings may suggest primary cortices may experience early development in early life, while the high-order cortex may change at a later stage. These findings provided insights into the heterogeneous development during early life and indicated the necessity of using an age-specific cortical parcellation in studying baby brains.