Department of Neurobiology, Weizmann Institute, 234 Herzl St, Rehovot 76100, Israel.
Hippocampus. 2013 Dec;23(12):1410-24. doi: 10.1002/hipo.22194. Epub 2013 Sep 22.
The multiple layers of medial entorhinal cortex (mEC) contain cells that differ in selectivity, connectivity, and cellular properties. Grid cells in layer II and in the deeper layers express triangular grid patterns in the environment. The firing rate of the conjunctive cells found in layer III and below, on the other hand, show grid-by-head direction tuning. In this study, we model the differentiation between grid and conjunctive cells in a network with self-organized connections. Arranged into distinct "layers", the model grid units and conjunctive units develop, with a similar time course, grid fields resulting from firing rate adaptation and competitive learning. Grid alignment in both layers is delayed with respect to the formation of triangular grids. A common grid orientation among conjunctive units is produced, in the model, by head-direction modulated collateral interactions, while the grids of grid units inherit the same orientation through connections from conjunctive units. Grid units as well as conjunctive units share a similar spacing but show a random distribution of spatial phases. Grid units however carry more spatial information than conjunctive units, thus providing better inputs for the hippocampus to form spatial memories.
内嗅皮层的多层结构（mEC）包含在选择性、连接性和细胞特性上存在差异的细胞。层 II 和更深层中的网格细胞在环境中表达三角形网格图案。另一方面，在层 III 及以下发现的联合细胞的发射率显示网格-头部方向调谐。在这项研究中，我们使用具有自组织连接的网络来模拟网格和联合细胞之间的分化。模型的网格单元和联合单元以相似的时间过程排列成不同的“层”，网格场是由发射率适应和竞争学习产生的。与三角形网格的形成相比，两层中的网格对齐都被延迟了。在模型中，通过头部方向调制的侧支相互作用产生了联合单元的共同网格方向，而通过来自联合单元的连接，网格单元继承了相同的方向。网格单元和联合单元具有相似的间距，但显示出空间相位的随机分布。然而，网格单元比联合单元携带更多的空间信息，从而为海马体形成空间记忆提供了更好的输入。
