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. Author manuscript; available in PMC: 2014 Jul 1.
Published in final edited form as: Wiley Interdiscip Rev Dev Biol. 2012 Sep 18;2(4):443–459. doi: 10.1002/wdev.88

Figure 4. Inside-out layer formation of excitatory neurons in the neocortex.

Figure 4

The PP is formed by the production of the first wave of post-mitotic neurons that migrate from the VZ to the pial surface. Then, a second wave of new-born neurons (blue triangles) migrate through the SVZ/IZ and split the PP into the more superficial MZ (neurons in the MZ are represented by orange ovals) and the more deeply located SP (neurons in the SP are represented by green diamonds), creating the CP – the future neocortex. Neurons generated subsequently (represented by triangles with different colors, pink, purple and yellow by birth order) expand the CP in an inside-out fashion, as later-born neurons pass the existing neurons to occupy more superficial layers. The VZ progressively shrinks as the neural progenitor cells decrease during later embryonic development. During the postnatal development towards adulthood, the SP degenerates and leaves behind a six-layered neocortex (panel on the right). CP: cortical plate; IZ: intermediate zone; MZ: marginal zone; PP: preplate; SP: subplate; SVZ: subventricular zone; VZ: ventricular zone; WM: white matter.