Expression patterns of layer-specific markers in normal human temporal cortex. Adjacent tissue sections were either immunolabeled for NeuN, all layers (a), calbindin, mainly layer II (b), SMI32, layers III and V (c) and parvalbumin, mainly layer IV (e) or processed for ISH for RORß, layer IV (d), and ER81, layer V (f) mRNAs. (a) NeuN staining shows the six neocortical layers indicated by Roman numerals. (b) Calbindin-positive interneurons are mainly located in layer II and to a lesser extent in layer III-IV (c) SMI32-positive neurons are located in layer III and layer V/VI. There is always a clear demarcation of layer IV in terms of a SMI32-free area between layer III and V. The apical dendrites of SMI32-positive neurons in layer III have a parallel orientation and reach the lower border of layer I. (d) The typical appearance of RORß mRNA-positive neurons is a dense band on the level of layer IV, organised in small columns and with an extension of less dense RORß-positive “branches” into the neighbouring layers III and V. (e) Parvalbumin-positive interneurons are mainly seen in layer IV of the human neocortex. At this level they form a well visible fiber plexus which refers to the parvalbumin staining in neurites and parvalbumin-containing synaptic terminals. (f) Strongly stained ER81 mRNA-expressing neurons are always seen in an infra-granular position. In the subcortical white matter, however, no abundance of ER81-positive neurons is observed in the control group. Additionally, a faint and variable ER81-staining is seen in pyramidal neurons of layer III. Scale bars: 250 μm.