Olsen Grethe M, Ohara Shinya, Iijima Toshio, Witter Menno P
The Faculty of Medicine, Kavli Institute for Systems Neuroscience, Centre for Neural Computation, Egil and Pauline Braathen and Fred Kavli Centre for Cortical Microcircuits, NTNU - Norwegian University of Science and Technology, Postbox 8905, 7491, Trondheim, Norway.
Division of Systems Neuroscience, Tohoku University Graduate School of Life Sciences, Katahira 2-1-1, Aoba-Ku, Sendai, 980-8577, Japan.
Hippocampus. 2017 Apr;27(4):335-358. doi: 10.1002/hipo.22701. Epub 2017 Jan 16.
The posterior parietal cortex has been implicated in spatial functions, including navigation. The hippocampal and parahippocampal region and the retrosplenial cortex are crucially involved in navigational processes and connections between the parahippocampal/retrosplenial domain and the posterior parietal cortex have been described. However, an integrated account of the organization of these connections is lacking. Here, we investigated parahippocampal connections of each posterior parietal subdivision and the neighboring secondary visual cortex using conventional retrograde and anterograde tracers as well as transsynaptic retrograde tracing with a modified rabies virus. The results show that posterior parietal as well as secondary visual cortex entertain overall sparse connections with the parahippocampal region but not with the hippocampal formation. The medial and lateral dorsal subdivisions of posterior parietal cortex receive sparse input from deep layers of all parahippocampal areas. Conversely, all posterior parietal subdivisions project moderately to dorsal presubiculum, whereas rostral perirhinal cortex, postrhinal cortex, caudal entorhinal cortex and parasubiculum all receive sparse posterior parietal input. This indicated that the presubiculum might be a major liaison between parietal and parahippocampal domains. In view of the close association of the presubiculum with the retrosplenial cortex, we included the latter in our analysis. Our data indicate that posterior parietal cortex is moderately connected with the retrosplenial cortex, particularly with rostral area 30. The relative sparseness of the connectivity with the parahippocampal and retrosplenial domains suggests that posterior parietal cortex is only a modest actor in forming spatial representations underlying navigation and spatial memory in parahippocampal and retrosplenial cortex. © 2017 Wiley Periodicals, Inc.
后顶叶皮层与包括导航在内的空间功能有关。海马旁回和海马旁区域以及压后皮质在导航过程中起着关键作用，并且已经描述了海马旁回/压后区域与后顶叶皮层之间的连接。然而，缺乏对这些连接组织的综合描述。在这里，我们使用传统的逆行和顺行示踪剂以及用改良狂犬病毒进行的跨突触逆行示踪，研究了每个后顶叶亚区和相邻的二级视觉皮层与海马旁回的连接。结果表明，后顶叶皮层以及二级视觉皮层与海马旁回区域整体连接稀疏，但与海马结构没有连接。后顶叶皮层的内侧和外侧背部分区从所有海马旁回区域的深层接收稀疏输入。相反，所有后顶叶亚区都适度投射到背侧前下托，而吻侧嗅周皮层、嗅后皮层、尾侧内嗅皮层和副下托都接收稀疏的后顶叶输入。这表明前下托可能是顶叶和海马旁回区域之间的主要联络点。鉴于前下托与压后皮质密切相关，我们在分析中纳入了后者。我们的数据表明，后顶叶皮层与压后皮质适度连接，特别是与吻侧30区。与海马旁回和压后区域连接的相对稀疏性表明，后顶叶皮层在形成海马旁回和压后皮质中导航和空间记忆的空间表征方面只是一个适度的参与者。©2017威利期刊公司。
