The term area 1 of Brodmann (guenon) refers to a subdivision of the postcentral gyrus of the guenon defined on the basis of cytoarchitecture. Brodmann-1909 regarded it as topologically and cytoarchitecturally homologous to the area 1 of Brodmann (human). Distinctive features ( Brodmann-1905 ): the molecular layer of the cerebral cortex (I) is cell free; the external granular layer (II) contains a population composed primarily of granule cells superfically with some small pyramidal cells and stellate cells in its deeper portion; the most densely populated layer is the internal granular layer (IV) which contains small round darkly stained cells with little cytoplasm and larger pyramidal cells or stellate cells sparsely intermixed; the internal pyramidal layer (V), relatively wide and distinct ly bounded by layer IV and the multiform layer (VI), has a dense population of medium sized ganglion cells and pyramidal cells concentrated along its border with layer IV and a clear sublayer 5b containing fewer and smaller cells adjacent to layer VI; layer VI has an abundant neuronal population that is divisible into a sublayer 6a composed primarily of medium sized triangular and larger pyramidal cells, and a deeper sublayer 6b composed strictly of small fusiform cells that are less densely distributed; layer VI is quite wide and it merges gradually with the subcortical white matter.