Kavli Institute for Systems Neuroscience and Centre for Neural Computation, Norwegian University of Science and Technology, 7489, Trondheim, Norway.
J Comp Neurol. 2014 Mar;522(4):772-93. doi: 10.1002/cne.23442.
The parahippocampal region, which comprises the perirhinal, postrhinal, and entorhinal cortices, as well as the pre- and parasubiculum, receives inputs from several association cortices and provides the major cortical input to the hippocampus. This study examined the topographic organization of projections from the orbitofrontal cortex (OFC) to the parahippocampal region in rats by injecting anterograde tracers, biotinylated dextran amine (BDA) and Phaseolus vulgaris-leucoagglutinin (PHA-L), into four subdivisions of OFC. The rostral portion of the perirhinal cortex receives strong projections from the medial (MO), ventral (VO), and ventrolateral (VLO) orbitofrontal areas and the caudal portion of lateral orbitofrontal area (LO). These projections terminate in the dorsal bank and fundus of the rhinal sulcus. In contrast, the postrhinal cortex receives a strong projection specifically from VO. All four subdivisions of OFC give rise to projections to the dorsolateral parts of the lateral entorhinal cortex (LEC), preferentially distributing to more caudal levels of LEC. The medial entorhinal cortex (MEC) receives moderate input from VO and weak projections from MO, VLO, and LO. The presubiculum receives strong projections from caudal VO but only weak projections from other OFC regions. As for the laminar distribution of projections, axons originating from OFC terminate more densely in upper layers (layers I-III) than in deep layers in the parahippocampal region. These results thus show a striking topographic organization of OFC-to-parahippocampal connectivity. Whereas LO, VLO, VO, and MO interact with perirhinal-LEC circuits, the interactions with postrhinal cortex, presubiculum, and MEC are mediated predominantly through the projections of VO.
旁海马回区域包括了双侧嗅周皮质、后嗅皮质、内嗅皮质以及前、旁海马回，它接收来自多个联合皮质的输入，并向海马体提供主要的皮质输入。本研究通过向大鼠眶额皮质（OFC）的四个亚区注射顺行示踪剂生物素化葡聚糖胺（BDA）和菜豆植物凝集素（PHA-L），研究了来自眶额皮质的投射到旁海马回的拓扑组织。双侧嗅周皮质的前段接受来自内侧（MO）、腹侧（VO）和腹外侧（VLO）眶额区域以及外侧眶额区域的后段（LO）的强烈投射。这些投射终止于嗅沟的背侧缘和底部。相比之下，后嗅皮质接受来自 VO 的强烈投射。OFC 的所有四个亚区都向外侧内嗅皮质（LEC）的背外侧部分发出投射，优先分布在 LEC 的更后端。内侧内嗅皮质（MEC）从中侧 VO 接受中等输入，从 MO、VLO 和 LO 接受弱输入。前下托接受来自后段 VO 的强烈投射，但仅接受来自其他 OFC 区域的微弱投射。至于投射的层分布，来自 OFC 的轴突在旁海马回中比在深层更密集地终止于上层（I-III 层）。这些结果表明，OFC 到旁海马回的连接具有显著的拓扑组织。虽然 LO、VLO、VO 和 MO 与双侧嗅周皮质-LEC 回路相互作用，但与后嗅皮质、前下托和 MEC 的相互作用主要通过 VO 的投射来介导。
