Brodmann area 12 is a subdivision of the
cerebral cortex of the
guenon defined on the basis of
cytoarchitecture. It occupies the most rostral portion of the
frontal lobe. Brodmann-1909 did not regard it as
homologous, either
topographically or cytoarchitecturally, to
rostral area 12 of the human. Distinctive features (Brodmann-1905): a quite distinct internal
granular layer (IV) separates slender
pyramidal cells of the external pyramidal layer (III) and the internal pyramidal layer (V); the
multiform layer (VI) is expanded, contains widely dispersed
spindle cells and merges gradually with the underlying cortical
white matter; all cells, including the pyramidal cells of the external and internal pyramidal layers are inordinately small; the internal pyramidal layer (V) also contains spindle cells in groups of two to five located close to its border with the internal granular layer (IV).