Contribution of head-direction cells to path integration within grid cell networks

我们在日常活动中有效导航的能力依赖于内侧内嗅觉皮质的神经元。在这个大脑区域内，网格细胞提供了我们所处位置的内部表示。当我们在太空中移动时，网格单元会更新它们的位置估计，以反映我们的时刻位置，就像我们在行走时在GPS设备中更新当前位置一样。这个过程被称为路径整合，在网格细胞的情况下，取决于我们的方向和行走速度的整合。目前的网格细胞计算模型认为，航向信息来自第二种类型的神经元，称为头部方向(HD)神经元。每个HD细胞只有在动物头部指向特定方向时才是活跃的，不同的HD细胞具有不同的优先方向。尽管有大量的计算模型解释了网格细胞的路径整合，但我们对路径整合的理解仍然不完整，原因至少有两个。首先，没有明确的实验证据表明HD细胞的活动控制着路径整合的方向性成分。其次，HD细胞群体中的异质性和复杂性被低估了。例如，所有模型都假设HD细胞形成一个同质的群体，但我们最近的实验表明情况并非如此。本研究项目的总体目标是调查HD细胞是否以及如何对路径整合做出贡献。我们将解决以下两个问题：1)网格细胞网络中路径整合的角度成分是否受头向细胞的活动控制？2)内侧嗅觉皮质中所有HD细胞的优先方向是否依赖于丘脑区HD细胞的输入？我们将通过同时记录HD细胞和网格细胞，并使用光遗传学技术来操纵主要的丘脑HD输入到皮质来回答这些问题。

Our ability to navigate efficiently during our daily activities depends on neurons of the medial entorhinal cortex. Within this brain area, grid cells provide an internal representation of our location. When we move in space, grid cells update their location estimate to reflect our moment-to-moment position, much like our current location is updated in a GPS device as we walk. This process is called path integration and, in the case of grid cells, depends on the integration of our heading and walking speed. Current computational models of gridcells propose that heading information comes from inputs from a second type of neurons called head-direction (HD) cells. Each HD cell is active only when the head of an animal points in a specific direction, with different HD cells having different preferred directions.Despite the abundance of computational models explaining path integration by grid cells, our understanding of path integration is still incomplete for at least two reasons. First, there is no clear experimental evidence that the activity of HD cell controls thedirectional component of path integration. Second, the level of heterogeneity and complexity within the HD cell population is underestimated. For example, all models assume that HD cells form a homogeneous population, but our recent experiments indicate that this is not the case. The general aim of this research project is toinvestigate whether and how HD cells contribute to path integration. We will address the following two questions: 1) Is the angular component of path integration in grid cell network controlled by the activity of head-direction cells? 2) Does the preferred direction of all HD cells in the medial entorhinal cortex depend on inputs from HD cells in thalamic areas? We will answer these questions by performing simultaneous recordings from HD cells and grid cells, and by employing optogenetic techniques to manipulate the main thalamic HD inputs to the cortex.