Van Groen Thomas, Wyss J Michael
Department of Neuroscience and Neurology, University of Kuopio, FIN 70211 Kuopio, Finland.
J Comp Neurol. 2003 Aug 25;463(3):249-63. doi: 10.1002/cne.10757.
Although the retrosplenial granular b cortex (Rgb) is situated in a critical position between the hippocampal formation and the neocortex, surprisingly few studies have examined its connections carefully. The present experiments use both anterograde and retrograde tracing techniques to characterize the connections of Rgb. The main cortical projections from Rgb are to the caudal part of the anterior cingulate cortex, area 18b, retrosplenial granular a cortex (Rga), and postsubiculum, and less dense terminal fields are present in the prelimbic and caudal occipital cortices. The major subcortical projections are to the anterior thalamic nuclei and the rostral pontine nuclei, and very small terminal fields are present in the caudal dorsomedial part of the striatum, the reuniens and reticular nuclei of the thalamus, and the mammillary bodies. Contralaterally, Rgb primarily projects to itself, i.e., homotypically, and more sparsely projects to Rga and postsubiculum. In general, the axons from Rgb terminate ipsilaterally in cortical layers I and III-V and contralaterally in layer V, with a smaller number of terminals in layers I and VI. Thalamic projections from Rgb target the anteroventral and laterodorsal nuclei of the thalamus, with only a few axons terminating in the anterodorsal nucleus, the reticular nucleus, and the nucleus reuniens of the thalamus. Rgb is innervated by the anterior cingulate cortex, precentral agranular cortex, cortical area 18b, dorsal subiculum, and postsubiculum. Subcortical projections to Rgb originate mainly in the claustrum, the horizontal limb of the diagonal band of Broca, and the anterior thalamic nuclei. These data demonstrate that, in the rat, Rgb is a major nodal point for the integration and subsequent distribution of information to and from the hippocampal formation, the midline limbic and visual cortices, and the thalamus. Thus, similarly to the entorhinal cortex, Rgb in the rat is a prominent gateway for information exchange between the hippocampal formation and other limbic areas of the brain.
尽管压后颗粒b皮质（Rgb）位于海马结构和新皮质之间的关键位置，但令人惊讶的是，很少有研究仔细研究其连接情况。本实验使用顺行和逆行追踪技术来描述Rgb的连接。Rgb的主要皮质投射是到前扣带皮质的尾部、18b区、压后颗粒a皮质（Rga）和后下托，在前边缘皮质和枕叶尾部皮质中存在较稀疏的终末场。主要的皮质下投射是到丘脑前核和脑桥嘴侧核，在纹状体的尾背内侧部分、丘脑的 reunien核和网状核以及乳头体中存在非常小的终末场。在对侧，Rgb主要投射到其自身，即同型投射，并且更稀疏地投射到Rga和后下托。一般来说，来自Rgb的轴突在同侧终止于皮质I层和III - V层，在对侧终止于V层，在I层和VI层中的终末较少。来自Rgb的丘脑投射靶向丘脑的前腹侧核和外侧背核，只有少数轴突终止于丘脑的前背核、网状核和reunien核。Rgb接受前扣带皮质、中央前无颗粒皮质、18b区皮质、背侧下托和后下托的神经支配。到Rgb的皮质下投射主要起源于屏状核、Broca斜带的水平支和丘脑前核。这些数据表明，在大鼠中，Rgb是信息整合以及随后在海马结构、中线边缘和视觉皮质以及丘脑之间信息分布的主要节点。因此，与内嗅皮质类似，大鼠中的Rgb是海马结构与大脑其他边缘区域之间信息交换的重要通道。
