A century of progress in corticoneurogenesis: from silver impregnation to genetic engineering.

Within the past 125 years, we have witnessed great strides in understanding development and evolution of the cerebral cortex, arguably the structure that makes us human. Among the distinguishing features of cortical development are discoveries that its constituent neurons are not generated locally and that after assuming their proper areal, radial, and laminar position, they serve the individual throughout the lifespan. Although the basic cellular events and all major developmental phenomena have been discovered by the use of classical methods, advents of new, evermore sophisticated experimental methods that range from neuroimaging to molecular genetics enable elucidation of the molecular and cellular mechanisms underlying evolutionary elaboration of the cortex and opens the possibility for the prevention and treatment of congenital disorders of the highest cognitive functions in humans.