15 × 0.15 × 0.5 mm/voxel), () (0.25 × 0.25 × 1.0 mm/voxel), and () (0.25 × 0.30 × 1.0 mm/voxel) are from MRI scans of fixed brains at different developmental stages showing the parietal lobe in a coronal section. Higher signal intensities represent greater density of cellular material. They illustrate both the rapid growth and differentiation of the cortex. At 11.5 PCW () three layers can be identified in the cerebral wall; the proliferative layer (inner, white) and cortical plate (outer, white) separated by the intermediate/subplate zone. At 14.5 () and 17 PCW () four layers can be seen. Layer1 is very thin and not discernible everywhere and is probably the VZ. Layer 2 corresponds to the subventricular/intermediate zones and layer 3 to the subplate (as observed at 18 PCW by ) and 4 is the cortical plate. ( and ) The entire cross-section of the cortex at 16 PCW. Nissl staining shows the different zones in the cerebral wall. The cell rich and cell poor layers in the SVZ first seen at 12.5 PCW are more pronounced by 16 PCW. Er81 immunostaining is found in cell nuclei the VZ and SVZ (), and at high density in a layer in the middle of the cortical plate likely to be layer V (see text). This is shown in close-up in (). CR immunoreactivity has a different location, being intense in the marginal zone (cell bodies and neurites) with CR-positive cell bodies in the cortical plate located mainly in a putative layer IV (). In addition, lower power images (, ) show dense PAX6 immunoreactivity in cell nuclei throughout the VZ and SVZ at this stage of development which coincides with GFAP immunoreactivity visible in cell bodies in the VZ and ISVZ but mostly localized to radial fibers in the rest of the SVZ. IZ intermediate zone; IFL, intermediate fiber layer. Scale bar = 5 mm in , 500 μm in , , , and 200 μm in , , .Copyright information:Taken from "A Molecular Neuroanatomical Study of the Developing Human Neocortex from 8 to 17 Postconceptional Weeks Revealing the Early Differentiation of the Subplate and Subventricular Zone"Cerebral Cortex (New York, NY) 2007;18(7):1536-1548.Published online 26 Oct 2007PMCID:PMC2430151.