Figure 3. Direct and indirect neurogenic pathways during corticogenesis.
(a) The neocortex is built in an inside-out manner in which neurons born from deeply located germinal zone migrate past earlier-born neurons to reside in more superficial layers. Note that initially, the preplate (PP) is split into a subplate (SP) and superficially located marginal zone (MZ) by incoming L6 neurons, such that early born neurons are later found in L1. Direct neurogenesis from the ventricular zone (VZ) predominates at early developmental stages, while indirect neurogenesis from the subventricular zone (SVZ) progressively increases during corticogenesis. E: Embryonic day; MZ: marginal zone; PP: preplate; SP: subplate. (b) FlashTag (FT) labelling highlights neurons born in the VZ through direct neurogenesis (ref. 55).