Defined neuronal cell types in the lateral entorhinal cortex supporting object and space coding

我们日常经历的记忆，即所谓的情景记忆，是由海马体和各种新皮层区域之间的相互作用产生的。人们普遍认为情景记忆由三个主要组成部分组成：视觉空间信息流（“哪里”部分），关于物体和事件的信息流（“什么”部分），以及时间信息流（“何时”部分）。从概念上讲，“哪里”成分支持情景记忆的空间表征，而“什么”和“何时”成分与非空间表征相关。一种假设认为内侧内嗅皮层（MEC）传达空间表征，而外侧内嗅皮层（LEC）传达非空间表征。然而，这种简单的二分法必须加以修正。最近发现，LEC神经元也表现出空间编码特性，如果环境中充满了物体，反之亦然，MEC中有细胞对气味或视觉线索的变化做出反应。此外，基于病毒介导的跟踪，我们确定了新的mesamatergic和GABA能的预测MEC的LEC，强烈暗示MEC-LEC的串扰之前，在海马整合的信息。与在过去十年中被广泛研究的MEC不同，对LEC中的神经元网络以及它们的活动如何受到不同输入的调制知之甚少。基于分子标记物的表达，轴突投射模式和气味反应，我们已经确定了两种不同的神经元细胞类型/合奏LEC。在这里，我们建议研究这些合奏的目的是更好地了解他们的贡献编码的空间和非空间组件的经验，并最终的作用LEC情景记忆。

The memory of our daily experiences, so-called episodic memory, is generated by interactions between the hippocampus and various neocortical regions. It is widely assumed that episodic memory consists of three main components: the visual-spatial information stream (the “where” component), the information stream about objects and events (the “what” component), and the temporal information stream (the “when” component). Conceptually, the “where” component supports spatial representations of episodic memories, while the “what” and “when” components are associated with non-spatial representation. One hypothesis posits that the medial entorhinal cortex (MEC) conveys spatial representations, while the lateral entorhinal cortex (LEC) conveys non-spatial representations. However, this simplified dichotomy must be revised. It was recently found that LEC neurons also demonstrate spatial coding properties if the environment is enriched with objects, and vice versa, there are cells in the MEC that are responsive to odours or changes in visual cues. Furthermore, based on virus-mediated tracing, we identified novel glutamatergic and GABAergic projections from the MEC to the LEC that are strongly suggestive for MEC-LEC cross-talk before integration of the information in the hipopcampus. Unlike the MEC that has been extensively studied over the last decade, much less is known about neuronal networks in the LEC and how their activity is modulated by different inputs. Based on molecular marker expression, axonal projection pattern and odour responsiveness, we have identified two distinct neuronal cell types/ensembles in the LEC. Here we propose to study these ensembles with the aim to better understand their contribution for coding of spatial and non-spatial components of an experience, and ultimately the role of the LEC for episodic memory.