van Groen T, Wyss J M
Department of Cell Biology and Anatomy, University of Alabama, Birmingham 35294.
Brain Res. 1990 Oct 8;529(1-2):165-77. doi: 10.1016/0006-8993(90)90824-u.
The hippocampal formation contributes importantly to many cognitive functions, and therefore has been a focus of intense anatomical and physiological research. Most of this research has focused on the hippocampus proper and the fascia dentata, and much less attention has been given to the subicular cortex, the origin of most extrinsic projections from the hippocampal formation. The present experiments demonstrate that the postsubiculum is a distinct area of the subicular cortex. The major projections to the postsubiculum originate in the hippocampal formation, the cingulate cortex, and the thalamus (primarily from the anterodorsal (AD) nucleus and to a lesser extent from the anteroventral (AV) and lateral dorsal (LD) nuclei). These projections differ from the thalamic projections to presubiculum and parasubiculum. Efferent projections from the postsubiculum terminate in both cortical and subcortical areas. The cortical projections terminate in the subicular and retrosplenial cortices and in the caudal lateral entorhinal and perirhinal cortices. Subcortical projections primarily end in the AD and the LD nuclei of the thalamus. These thalamic projections end in areas that are distinct from those to which the presubiculum and parasubiculum project. For instance, the postsubiculum has a dense terminal field in the AD nucleus, but presubicular axons terminate predominantly in the AV nucleus. The cortical projections also distinguish postsubiculum. All subicular areas project to the entorhinal cortex, but the postsubicular projection ends in the deep layers (i.e. IV-VI), whereas presubiculum projects to layers I and III, and parasubiculum projects to layer II. Postsubiculum projects to retrosplenial granular b cortex and only incidentally to retrosplenial granular a cortex. In contrast presubiculum projects to the retrosplenial granular a cortex but not to the retrosplenial granular b cortex. These differences clearly mark the postsubiculum, the presubiculum, and the parasubiculum as distinct regions within the subicular cortex and suggest that they subserve different roles in the processing and integration of limbic system information.
海马结构对多种认知功能起着重要作用，因此一直是解剖学和生理学深入研究的焦点。大部分此类研究集中在海马本身和齿状回，而对海马结构大部分外在投射的起源——下托皮质的关注则少得多。目前的实验表明，后下托是下托皮质的一个独特区域。投射到后下托的主要纤维起源于海马结构、扣带皮质和丘脑（主要来自前背核，其次来自前腹核和外侧背核）。这些投射与投射到前下托和旁下托的丘脑投射不同。后下托的传出投射终止于皮质和皮质下区域。皮质投射终止于下托和压后皮质以及尾侧外侧内嗅皮质和嗅周皮质。皮质下投射主要终止于丘脑的前背核和外侧背核。这些丘脑投射终止的区域与前下托和旁下托投射的区域不同。例如，后下托在丘脑前背核有密集的终末野，而前下托的轴突主要终止于前腹核。皮质投射也使后下托具有独特性。所有下托区域都投射到内嗅皮质，但后下托的投射终止于深层（即IV - VI层），而前下托投射到I层和III层，旁下托投射到II层。后下托投射到压后颗粒b皮质，仅偶尔投射到压后颗粒a皮质。相反，前下托投射到压后颗粒a皮质，但不投射到压后颗粒b皮质。这些差异清楚地将后下托、前下托和旁下托标记为下托皮质内的不同区域，并表明它们在边缘系统信息的处理和整合中发挥不同作用。
