The term area 23 of Brodmann (human) refers to a subdivision of the cytoarchitecturally defined cingulate region of cerebral cortex. In the human it occupies most of the posterior cingulate gyrus adjacent to the corpus callosum. At the caudal extreme it is bounded approximately by the parieto-occipital sulcus. Cytoarchitecturally it is bounded dorsally by the area 31 of Brodmann (human), rostrally by the area 24 of Brodmann (human), and ventrorostrally in its caudal half by the retrosplenial area ( Brodmann-1909 ).