The term area 6 of Brodmann (guenon) refers to a cytoarchitecturally defined portion of the frontal lobe of the guenon. Brodmann-1909 regarded it as topographically and cytoarchitecturally homologous to the area 6 of Brodmann (human) and noted that in the monkey area 4 is larger than area 6, while in the human area 6 is larger than area 4. Distinctive features ( Brodmann-1905 ): it is thick relative to other cortical areas; the transition from cortex to subcortical white matter is gradual; cell layers are indistinct; and the internal granular layer (IV) is absent.