(Götz and Huttner, 2005; Kriegstein et al., 2006). Initially, RGs generate neurons directly (‘direct neurogenesis’), but begin producing a second population of neural precursors called intermediate progenitors (IPs) around E13.5 (Hendelman, 1991). The late phase of corticogenesis is dominated by an expansion of the pool of RG-derived IPs in the subventricular zone (SVZ) which undergo limited rounds of division to produce neurons (‘indirect neurogenesis’).
