The hippocampal formation is critically involved in learning and memory, and contains a large proportion of neurons encoding aspects of the organism's spatial surroundings. In the medial entorhinal cortex (MEC), this includes grid cells with their distinctive hexagonal firing fields, as well as a host of other functionally defined cell types including head-direction cells, speed cells, border cells, and object vector cells. Such spatial coding emerges from the processing of external inputs by local microcircuits. However, it remains unclear exactly how local microcircuits and their dynamics within the MEC contribute to spatial discharge patterns. In this review we focus on recent investigations of intrinsic MEC connectivity, which have started to describe and quantify both excitatory and inhibitory wiring in the superficial layers of the MEC. Although the picture is far from complete, it appears that these layers contain robust recurrent connectivity that could sustain the attractor dynamics posited to underlie grid-pattern formation. These findings pave the way to a deeper understanding of the mechanisms underlying spatial navigation and memory.

中文翻译：

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内侧内嗅皮层空间编码微电路

海马结构与学习和记忆密切相关，并且包含大部分编码有机体空间环境方面的神经元。在内侧内嗅皮层 (MEC) 中，这包括具有独特六边形发射场的网格细胞，以及许多其他功能定义的细胞类型，包括头部方向细胞、速度细胞、边界细胞和对象矢量细胞。这种空间编码来自本地微电路对外部输入的处理。然而，目前尚不清楚MEC内的局部微电路及其动态如何影响空间放电模式。在这篇综述中，我们关注最近对内在 MEC 连接性的研究，这些研究已经开始描述和量化 MEC 表层中的兴奋性和抑制性布线。虽然图片远未完成，但似乎这些层包含强大的循环连接，可以维持假定为网格图案形成基础的吸引子动力学。这些发现为更深入地了解空间导航和记忆的机制铺平了道路。