Pigment architecture of the human telencephalic cortex. III. Regio praesubicularis.

Cortical lamination and parcellation of the human presubicular region is described with the aid of stereomicroscopical analysis of pigment preparations up to 1000 micrometers thick. The region can be subdivided into three major territories each of which is strongly influenced by the adjoining cortical tissue. The three subregions are: 1) the presubiculum sensu stricto. It lies near the subiculum at its medial margin and can be subdivided into 6 areas. 2) the parasubiculum. It borders on the entorhinal region and is composed of 5 areas. 3) the transsubiculum. It forms a transitional zone between allocortical and isocortical fields and consists of 3 areas. The presubicular region is characterized by a conspicuous layer of small and densely packed cells which--except the marginal parts of the subiculum--does not appear outside this region. Besides this autochthonous parvopyramidal layer, the presubicular cortex is composed of "foreign" cell layers which penetrate in varying number and to a varying extent into the region from the surrounding fields. The presubicular cortex shows extensive and incessant local variations, in so far as each one of its layers is very variable in breadth. In spite of this, a reliable parcellation can be achieved when only those layers are taken into consideration whose marginal parts are clearly recognizable. Hence, the proposed parcellation is based on the changing pattern of lamination which is depicted in diagrams for easy recognition of the various areas.