Brodmann area 18, or BA18, is part of the occipital cortex in the human brain. It accounts for the bulk of the volume of the occipital lobe. It is known as a "Visual Association Area" or V2 and is a first stage in processing or feature extraction of retinotopic images from V1.
Brodmann area 18 is a subdivision of the cerebral cortex of the guenon defined on the basis of cytoarchitecture. It is topographically and cytoarchitecturally homologous to parastriate area 18 of the human (Brodmann-1909). Distinctive features (Brodmann-1905): a wide, dense internal granular cell layer (IV); a distinct sublayer 3b of closely packed large pyramidal cells positioned in the external pyramidal layer (III) directly above layer IV; an almost cell-free, narrow internal pyramidal layer (V) with no larger ganglion cells; a very narrow, dense multiform layer (VI) composed of small polymorphic cells that form a distinct boundary with the underlying subcortical white matter. Like area 17 of Brodmann-1905, area 18 is relatively thin, with the three deep layers thin relative to the three outer layers, and has distinct boundaries between layers, abundance of granule cells, narrow layer VI, and sharp boundary between cortex and subcortical white matter.
