Abstract：
The hippocampal formation and entorhinal cortex are crucially involved in learning and memory as well as in spatial navigation. The conservation of these structures across the entire mammalian lineage demonstrates their importance. Information on a diverse set of spatially tuned neurons has become available, but we only have a rudimentary understanding of how anatomical network structure affects functional tuning. Bats are the only order of mammals that have evolved true flight, and with this specialization comes the need to navigate and behave in a three dimensional (3D) environment. Spatial tuning of cells in the entorhinal-hippocampal network of bats has been studied for some time, but whether the reported tuning in 3D is associated with changes in the entorhinal-hippocampal network is not known. Here we investigated the entorhinal-hippocampal projections in the Egyptian fruit bat (Rousettus aegyptiacus), by injecting chemical anterograde tracers in the entorhinal cortex. Detailed analyses of the terminations of these projections in the hippocampus showed that both the medial and lateral entorhinal cortex sent projections to the molecular layer of all subfields of the hippocampal formation. Our analyses showed that the terminal distributions of entorhinal fibers in the hippocampal formation of Egyptian fruit bats-including the proximo-distal and longitudinal topography and the layer-specificity-are similar to what has been described in other mammalian species such as rodents and primates. The major difference in entorhinal-hippocampal projections that was described to date between rodents and primates is in the terminal distribution of the DG projection. We found that bats have entorhinal-DG projections that seem more like those in primates than in rodents. It is likely that the latter projection in bats is specialized to the behavioral needs of this species, including 3D flight and long-distance navigation.
摘要：
海马结构和内嗅皮层在学习和记忆以及空间导航中起着至关重要的作用。这些结构在整个哺乳动物谱系中的保守性证明了它们的重要性。关于一组不同的空间调谐神经元的信息已经变得可用，但是我们对解剖网络结构如何影响功能调节只有初步的了解。蝙蝠是唯一进化出真正飞行的哺乳动物，随着这种专业化，需要在三维（3D）环境中进行导航和行为。蝙蝠的内嗅-海马网络中细胞的空间调整已经研究了一段时间，但报道的3D调谐是否与内嗅-海马网络的变化相关尚不清楚。在这里，我们研究了埃及果蝙蝠（Rousettusaegyptiacus）的内嗅-海马突起，通过在内嗅皮层注射化学顺行示踪剂。对海马中这些投影终止的详细分析表明，内侧和外侧内嗅皮层都将投影发送到海马结构所有子场的分子层。我们的分析表明，埃及果蝙蝠海马结构中内嗅纤维的末端分布-包括近端和纵向形貌以及层特异性-与其他哺乳动物物种（例如啮齿动物和灵长类动物）中描述的相似。迄今为止，啮齿动物和灵长类动物之间的内嗅-海马投射的主要差异在于DG投射的末端分布。我们发现蝙蝠的内嗅-DG投影看起来更像灵长类动物，而不是啮齿动物。蝙蝠的后一种投射很可能是专门针对该物种的行为需求，包括3D飞行和长途导航。
