Development of the Primate Cerebral Cortex

Abstract

The cerebral cortex is the crowning achievement of evolution and the biological substrate of human cognitive abilities. Although the basic principles of cortical development in all mammals are similar, the modifications of developmental events during evolution produce not only quantitative but also qualitative changes. Human cerebral cortex, as in the other species, is organized as a map in which specific cell classes are positioned into a radial, laminar, and areal array that depends on the sequential production and phenotypic specification of those cells and the directed migration from their place of origin to their distant final destination. The long and curvilinear migration pathways in the fetal human cerebrum depend critically on the stable radial glial scaffolding. After neurons assume their proper areal and laminar position, they attach locally and develop numerous proximal and long-distance connections that involve specific adhesion molecules, neurotransmitters, and receptors. However, the final pattern of synaptic connections is selected through functional validation and selective elimination of the initially overproduced neurons, axons, and synapses. In this review, the development of the cerebral cortex is described in the context of the radial unit hypothesis, the postulate of an embryonic protomap, and the concept of competitive neural interactions that ultimately create a substrate for the highest cognitive functions.