Expression patterns of layer-specific markers in FCD cases originating from the temporal or frontal lobe. (a-d) FCD IIIa; temporal. (e-h) FCD IIa, temporal; (i-l) FCD IIa, frontal. Representative micrographs of NeuN- (a,e,i) and SMI32-immunostained (c,g,k) sections or ISH for RORß (b,f,j) and ER81 (d,h,l) mRNAs are shown. Scale bar in a (valid for all micrographs): 250 μm. (a-d). FCD III; a temporal. (a) In this patient a clear hexalamination with strong columnisation is discernible. (b) Layer IV contains a dense band of RORß-positive neurons with columnar distribution. (c) Density of SMI32-positive neurons appears reduced in layer III. (d) Abundance of ER81 mRNA-positive neurons is similar to the control. (e-h) FCD IIa, temporal; (e) In this patient, NeuN staining shows a “hypoplastic” layer IV and a blurred transition between layer V and VI. (f) A slim layer IV with only a few RORß mRNA-positive neurons is present. RORß-positive “branches” in layer III and V as seen in (b) are not detectable. (g) SMI32-positive neurons appear severely reduced. In layer III several large and dysmorphic SMI32-positive neurons are visible. Note that SMI-positive neurons have a parallel orientation of their apical dendrites and are in a correct position sparing layer IV. (h) Strong rarefication of ER81 mRNA expressing neurons in layer V. (i-l) FCD IIa, frontal. (i) Note a severely disturbed laminar organization with a gradient from right to left. Several pyramidal cells have an abnormal large size. (j) RORß mRNA-positive neurons are dispersed without columnar arrangement. (k) SMI32-immunostaining shows mainly a bilaminar distribution, which is disturbed in the left portion of the section where SMI32-positive neurons seem to “invade” layer IV (l). ER81 mRNA-positive neurons are abundant in layer V.