The term area 23 of Brodmann (guenon) refers to a subdivision of the cerebral cortex of the guenon defined on the basis of cytoarchitecture. Brodmann regarded it as topographically and cytoarchitecturally homologous to the combined area 23 of Brodmann (human) and area 23 of Brodmann (human) ( Brodmann-1909 ). Distinctive Features ( Brodmann-1905 ): the cortex is relatively thin; smaller cells predominate; the cell density of the multiform layer (VI) is great, producing a distinct boundary with the subcortical white matter; the internal granular layer (IV) is rather well developed; the internal pyramidal layer (V) contains a dense population of round, medium-sized ganglion cells concentrated at the border with layer IV; layers V and VI are narrow with a distinct mutual boundary.