The term paleocortex refers to one of three types of allocortex defined on the basis of cytoarchitecture. The other two are archicortex and periallocortex. It consists of very thin, primitive cortex with few clearly defined layers. It is distinguished developmentally by the fact that it does not develop through the cortical plate. It includes the main olfactory bulb, accessory main olfactory bulb, olfactory tubercle, septum, piriform cortex and periamygdalar area ( Stephan-1975 ). It differs from earlier definitions in that it includes the main olfactory bulb and accessory main olfactory bulb, which were once not recognized to be cortical structures. It constitutes less than 1% of the surface area of the cerebral cortex ( Stephan-1975, Zilles-1990 ).