1 Introduction Cortical development is a complex, tightly regulated process that eventually leads to the six-layered adult human neocortex, the substrate of the unique cognitive, emotional, and social abilities of our species. The basic mechanisms of early cortical development are believed to be very similar among mammals, which has led to a tendency of extrapolating experimental data from rodents on humans. Certain traits, such as the general pattern of forebrain regionalization and expression of region-speci?c genes, seem to be conserved among vertebrates (e. g., Kammermeier and Reichert...