4.14 - The Development and Evolutionary Expansion of the Cerebral Cortex in Primates

Abstract

The cerebral cortex is the crowning achievement of brain evolution and the biological substrate of human uniqueness. The techniques and concepts of modern neurobiology have given us many new insights into the developmental and evolutionary mechanisms involved in building the human cerebrum. Comparisons of the molecular and cellular events among developing human, non-human primate, and rodent embryos have revealed similarities as well as differences that are relevant for understanding the evolutionary expansion and elaboration of the cerebral cortex. Relatively small genetic differences between mammalian species are predominately expressed in the brain, and usually act during embryogenesis at the time of the progenitor’s exit from the cell cycle. In this article, the evolution of the cerebral cortex is viewed in the context of the radial unit hypothesis, the postulate of an embryonic protomap, and the concept of competitive neuronal interactions. Advances in understanding corticogenesis in the embryo provide hints of how spontaneous mutations that affect the early stages of corticogenesis may have played a role in determining the species-specific size and basic organization of the cerebral cortex.