In the classification of Filimonoff various types of cortical formations can be identified. The paleocortex (semicortex or cortex semi-separatus) is phyloge netic ally and ontogenetically the most ancient type of cortex and is characterized by an incomplete separation of the cortical lamina from the subcortical cellular aggregates. The archicortex or old cortex is characterized by a cortical lamina which has already become fully separated from the subcortex. It is, however, considerably less complex in its structure than that of the final stage of cortical evolution, the neocortex. Via so-called transitional cortex the archicortex
passes into the lower level of the intermediate or periarchicortex (the presubicular and entorhinal areas), whereas the neocortical lamina passes into the upper level of the latter (superlamination). As noted, the intermediate cortex. separating the ancient and old cortex from the new cortex, is divided correspondingly into two major zones which are termed peripaleocortical and periarchicortical formations (Fig. 1.2). It is emphasized that the new, ancient, and old cortex, sharply differing from each other in terms of cellular organization and stratification during the process of development, as well as in the adult organism, are not directly adjacent but are separated from each other by transitional areas which cannot be related either to the new, old, or ancient cortex and which we can single out, on this basis, as special areas which are termed the intermediate cortex.