Figure 7.

Systematic variation of embryonic layers in the prospective frontal cortex of the rat embryo (Nissl staining). Germinal zones and prospective cortical layers are named according to Bystron et al. (2008) and Reillo et al. (2011). a-d, Photomicrographs from a rat embryo of 16.5 days gestational age stained for Nissl. a, Low power photomicrograph at the level of the interventricular foramen shows the levels of photomicrographs b-d. b, The germinal zones of the prospective cingulate cortex next to the hippocampal formation (Hipp in a) are composed of the ventricular (VZ), the intermediate zone (IZ) which contains many cells migrating to the cortical plate, the subplate (SP), and the cortical plate (CP) which is thin. c, d, Prospective lateral areas have slightly thicker VZ with progressive thicker CP; the IZ contains many cells migrating to the CP. At this stage, a subventricular zone (SVZ) cannot be distinguished with Nissl stain. e-h, Photomicrographs from a rat embryo of 19.5 days gestational age stained for Nissl. e, Low power photomicrograph at the level of the anterior commissure (ca) shows the levels of photomicrographs f-h. f, The prospective cingulate area shows well differentiated VZ and SVZ. g, h, In a lateral direction, the VZ and the SVZ are slightly thicker, but a clear division of the SVZ into inner and outer zones is not apparent. Abbreviations: ca: anterior commissure; cc: corpus callosum; CP, cortical plate; Hipp: anterior extension of the hippocampal formation; IZ, intermediate zone; LGE, lateral ganglionic eminence; MGE, medial ganglionic eminence; MZ, marginal zone; Pir: piriform cortex in the primary olfactory cortex; SP, subplate; SVZ, subventricular zone; VZ, ventricular zone. Calibration bar in d applies to b-d; calibration bar in h applies to f-h. [Note: This figure is an examination of material from a gift of Dr. Alan Peters].