Temporal Organization of Memory in the Hippocampus

项目总结/摘要 情景记忆的特点是我们能够记住事件发生的时空背景 发生.大量证据表明海马神经元的活动反映了空间的表征 但是，直到最近，人们对海马神经元是否或如何编码时间知之甚少。然而，在这方面， 我们最近的研究表明海马神经元活动提供了时间背景信号， 有助于记忆。此外，在这个项目中大量积累的证据表明， 海马神经元--被称为时间细胞--在时间延长的经历中的特定时刻放电， 类似于海马定位细胞，其在空间延伸的 环境拟议的研究将继续探讨时间表征的性质， 海马系统和相关脑区。到目前为止，实验集中在时间细胞活动期间， 记忆事件之间的间隙，以便在没有动态的情况下识别明确的定时信号。 外部事件，同时保持位置和行为不变。在项目的下一阶段，我们将探索 时间细胞如何组织组成特定情节的一系列事件。此外，所有记录 海马时间细胞迄今为止仅在CA 1区进行了研究。我们将研究是否时间 编码仅限于CA 1或广泛存在于海马体和其他内侧颞叶和前额叶区域。 我们还将探讨是否时间序列是建立在固有的海马电路， 海马体内的时间编码依赖于来自皮层区域的输入。这些研究将挑战 海马系统致力于空间导航的流行观点， 理解这个系统如何在时空背景下表示事件。

PROJECT SUMMARY/ABSTRACT Episodic memory is characterized by our ability to remember the spatial and temporal context in which events occur. There is substantial evidence that the hippocampal neuronal activity reflects a representation of space but, until recently, little was known about whether or how the hippocampal neurons encode time. However, recent studies by us have shown that hippocampal neuronal activity provides a temporal context signal that contributes to memory. In addition there is now evidence, substantially accumulated in this project, that hippocampal neurons - called time cells - fire during particular moments in a temporally extended experience, similar to hippocampal place cells that fire associated with particular locations in a spatially extended environment. The proposed studies will continue to explore the nature of temporal representation by the hippocampal system and associated brain areas. Experiments so far have focused on time cell activity during a gap between remembered events in order to identify an unambiguous timing signal in the absence of dynamic external events and while holding place and behavior constant. In the next phase of the project we will explore how time cells organize a sequence of events that compose specific episodes. Also, all recordings of hippocampal time cells have so far been examined only in area CA1. We will examine whether temporal coding is limited to CA1 or widespread in the hippocampus and other medial temporal and prefrontal areas. We will also explore whether temporal sequencing is created within intrinsic hippocampal circuits or whether temporal coding within the hippocampus depends on inputs from cortical areas. These studies will challenge the prevalent view that the hippocampal system is dedicated to spatial navigation and advance our understanding of how this system represents events in their spatiotemporal context.