The term true isocortex refers to one of two types of neocortex. It is composed of the typical six layered cytoarchitecture of neocortex. The other type is proisocortex. Defined on the basis of cytoarchitecture, true isocortex is located predominantly in the frontal lobe, the temporal lobe, the parietal lobe, and the occipital lobe; it is present also in parts of the cingulate gyrus, the parahippocampal gyrus and the insula ( Stephan-1975; Zilles-1990 ).