Photomicrographs of coronal sections through the posterior cingulate cortex of the macaque monkey. This level includes areas 29, 30 and 23. (A) Nissl-stained section showing the laminar pattern of posterior cingulate cortex located just dorsal to the corpus callosum (cc). The layers of cortical area 23 are marked I to VI. (B) Immunostaining with plasma from a representative child with autism. As in the primary visual cortex, the most numerous labeled neurons are located in the superficial layers (I to III), although immunopositive neurons are located throughout all layers. This pattern was recapitulated in all cortical areas. Labeled cells were not observed in the cc, although apparent positive cells were observed in the subcortical white matter. Calibration bar, 250 μm.