Dynamics of gyrification in the human cerebral cortex during development

This study quantitatively characterized cortical gyrus folding over human neocortical development by calculating the gyrification index (GI) in 22 human fetal specimens from 16 to 40 weeks with magnetic resonance imaging data. GI values remained constant at approximately 1.0 until the fetal specimens reached 500 g body weight and 200 mm crown-rump length (CRL), respectively, and then increased in correlation with the body weight and CRL. The rostrocaudal GI distribution in the cerebral cortex revealed a correspondence of GI peaks with indentations of early-generated primary sulci at 21 weeks of gestation and more frequently increased GI values in the parieto-occipital region than in the fronto-temporal region at 31 and 40 weeks of gestation. These results provide a quantitative reference set for gyrification in normal human cortical development, which may help reveal the mechanism of neurodevelopmental disorders.