Kloosterman Fabian, Witter Menno P, Van Haeften Theo
Swammerdam Institute of Life Sciences, University of Amsterdam, Graduate School of Neurosciences Amsterdam, NL-1098 SM Amsterdam, The Netherlands.
J Comp Neurol. 2003 Jan 6;455(2):156-71. doi: 10.1002/cne.10472.
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.
在本研究中，我们详细分析了大鼠下托-海马旁回投射的拓扑组织。将顺行示踪剂菜豆凝集素-L和生物素化葡聚糖胺注射到下托不同的前后和横向水平。内嗅、嗅周和嗅后皮质的深层是下托投射的主要接受者，但在所有情况下我们都注意到一小部分投射也终止于浅层II和III。对海马旁回区域纤维模式的分析揭示了一种拓扑组织，这取决于下托细胞沿横向和前后轴的起源位置。起源于靠近CA1的下托细胞，即下托近端部分的投射，仅终止于外侧内嗅皮质和嗅周皮质。相比之下，来自更靠近下托-前下托边界的细胞，即下托远端部分的投射，终止于内侧内嗅皮质和嗅后皮质。此外，下托隔区的细胞投射到与嗅沟平行的内侧内嗅皮质外侧带以及嗅周或嗅后皮质，而更靠颞侧部分的细胞投射到内嗅皮质的更内侧部分。这些结果表明，下托向海马旁回区域的投射精确地对应了该区域向海马结构的已知输入。因此，我们认为下托与海马旁回区域之间的相互连接是作为平行通路组织起来的，这些通路用于分离信息流，从而保持所处理信息的一致性。尽管这种平行组织与CA1-海马旁回投射的平行组织相似，但在侧支化程度方面存在差异。
