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Topographical and laminar organization of subicular projections to the parahippocampal region of the rat
Author(s) -
Kloosterman Fabian,
Witter Menno P.,
Van Haeften Theo
Publication year - 2002
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.10472
Subject(s) - subiculum , entorhinal cortex , neuroscience , biotinylated dextran amine , hippocampal formation , anatomy , anterograde tracing , cortex (anatomy) , biology , hippocampus , perirhinal cortex , laminar organization , temporal lobe , axon , central nervous system , dentate gyrus , epilepsy
In this study, we analyzed in detail the topographic organization of the subiculoparahippocampal projection in the rat. The anterograde tracers Phaseolus vulgaris leucoagglutinin‐L and biotinylated dextran amine were injected into the subiculum at different septotemporal and transverse levels. Deep layers of the ento‐, peri‐, and postrhinal cortices are the main recipients of subicular projections, but in all cases we noted that a small fraction of the projections also terminates in the superficial layers II and III. Analysis of the fiber patterns in the parahippocampal region revealed a topographic organization, depending on the location of the cells of origin along both the transverse and the septotemporal axes of the subiculum. Projections originating from subicular cells close to CA1, i.e., proximal part of subiculum, terminate exclusively in the lateral entorhinal cortex and in the perirhinal cortex. In contrast, projections from cells closer to the subiculum‐presubiculum border, i.e., distal part of subiculum, terminate in the medial entorhinal cortex and in the postrhinal cortex. In addition, cells in septal portions of the subiculum project to a lateral band of entorhinal cortex parallel to the rhinal sulcus and to peri‐ or postrhinal cortices, whereas cells in more temporal portions project to more medial parts of the entorhinal cortex. These results indicate that subicular projections to the parahippocampal region precisely reciprocate the known inputs from this region to the hippocampal formation. We thus suggest that the reciprocal connectivity between the subiculum and the parahippocampal region is organized as parallel pathways that serve to segregate information flow and thus maintain the identity of processed information. Although this parallel organization is comparable to that of the CA1‐parahippocampal projections, differences exist with respect to the degree of collateralization. J. Comp. Neurol. 455:156–171, 2003. © 2002 Wiley‐Liss, Inc.