The term area 3 of Brodmann (guenon) refers to a cytoarchitecturally defined portion of cerebral cortex of the guenon that is located predominantly in the postcentral gyrus, but ventrally in a portion of the precentral gyrus as well. Brodmann-1909 regarded it as topographically and cytoarchitecturally homologous to area 3 of Brodmann (human). Distinctive features ( Brodmann-1905 ): compared to area 1 of Brodmann (guenon) and area 2 of Brodmann (guenon) the cortical thickness of area 3 is unusually thin, in fact, among the thinnest areas of the cerebral cortex; the cells of sublayer 3b of the external pyramidal layer (III) are smaller, plumper and more densely distributed in a tighter strip; cells of the internal granular layer (IV) are distributed more sparsely; the internal pyramidal layer (V) is relatively clear with scattered large to very large pyramid shaped ganglion cells separated by tangentially oriented fiber bundles; the multiform layer (VI) is composed of a dense population of homogeneously distributed cells such that sublayers are absent and the boundary with the subcortical white matter is distinct. According to Roberts-1963 the external granular layer (II), layer III and layer IV are not clearly demarcated from each other and are all densely packed with small cells.