The role of grid cell replay in navigation and memory consolidation

实验证据表明，海马体和相关的大脑区域与地点和事件的记忆有关。对动物的研究为这些功能提供了神经基础；具有空间调谐感受野的神经元。其中最广为人知的是海马定位细胞和内嗅网格细胞，它们似乎都是动物自我定位的信号。问题仍然存在。目前还不清楚，当动物计划在不久的将来的旅行路线时，这些神经元是如何参与的。此外，众所周知，海马体损伤会产生严重的记忆缺陷，但旧的记忆往往幸免，这表明它们的内容在大脑中被复制；这种效应被称为整合。同样，位置细胞和网格细胞在这一过程中的作用尚不清楚。尽管如此，导航规划和整合背后的潜在机制是重播；在定位细胞中发现的一种现象，在此过程中，细胞通过环境“模拟”轨迹。我们发现，网格细胞在回放过程中也会被招募，它们的活动通常落后于位置细胞。这支持了巩固过程中中继参与的概念，表明网格细胞将海马信息传递到皮层。我们还提出了一个计算模型，表明网格单元重放可能是计算路线的一种机制；一个简单的预测是，当动物做出导航选择时，重播应该发生。然而，回放分析要求很高，需要大量的神经元来准确解码信息内容。该项目的目的是使用两种光子显微镜在比以前更大的网格细胞群中记录重播，这将使网格重播在导航和整合中的参与能够更好地量化。其次，它将使我们能够区分来自内嗅皮层不同层的细胞的接合，这些细胞与海马体有不同的连接模式。

Experimental evidence links the hippocampus and related brain regions with memory for places and events. Investigations in animals provided a neural basis for these functions; neurons with spatially tuned receptive fields. The most widely recognized of which being hippocampal place cells and entorhinal grid cells, both of which appear to signal an animal's self-location. Questions remain. It is unclear how these neurons are engaged when an animal is planning routes to travel in the immediate future. Furthermore, it is known that hippocampal damage produces severe mnemonic deficits but that old memories are often spared, suggesting their content is duplicated in the brain; an effect known as consolidation. Again the role of place and grid cells in this process are unclear. None-the-less, a potential mechanism underlying both navigational planning and consolidation is replay; a phenomenon identified in place cells, during which the cells 'simulate' trajectories through the environment. We showed that grid cells are also recruited during replay, with their activity typically lagging behind place cells. This supports the notion of relay involvement in consolidation, suggesting the grid cells convey hippocampal information to the cortex.. We also proposed a computational model suggesting that grid cell replay may be a mechanism by which routes are calculated; a simple prediction being that replay should occur when animals make navigational choices. However, replay analyses are demanding and require large numbers of neurons to accurately decode the information content. The aims of this project are to use two photon microscopy to record replay in larger populations of grid cells than have previously been accessible, this will enable better quantification of the involvement of grid replay in navigation and consolidation. Secondarily it will enable us to distinguish the engagement of cells from different layers of the entorhinal cortex, which have distinct connectivity patterns with the hippocampus.