Cellular signatures of microstructural development in the human cerebral cortex

Motivation: The adolescent brain has been well described using MRI, revealing ongoing cortical thinning and volume loss. But which underlying cellular properties drive these changes?Goal(s): To model developmental patterns of soma and neurite architecture in the human cerebral cortex. Approach: We quantified in vivo cortical neurite and soma microstructure in a sample of children and adolescents aged 8-18 years. We then analysed two human gene expression databases to determine cell-type specific profiles underlying these MR-based changes. Results: Developmental increases in neurite density and reductions in soma radius suggest increasing cortical oligodendrocyte density, supporting the model of protracted intra-cortical myelination throughout the adolescent period. Impact: Our novel study suggests that ongoing intracortical myelination underpins developmental patterns of cortical neurite and soma microstructure. Once thought to be driven by synaptic pruning, increasing cortical oligodendrocyte density may underlie previously reported patterns of cortical volume loss in adolescence.