Temporal Organization of Memory in the Hippocampus

项目摘要/摘要 情节记忆的特点是我们能够记住事件发生的空间和时间背景 发生。有大量证据表明，海马神经元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， 我们最近的研究表明，海马神经元活动提供了一个时间背景信号， 对记忆有贡献。此外，现在有证据表明，在这个项目中积累了大量的 海马神经元--称为时间细胞--在时间延长的体验中，在特定的时刻被激发， 类似于在空间延伸的 环境。拟议的研究将继续探索时间表征的性质 海马体系统及相关脑区。到目前为止，实验主要集中在时间细胞活动上 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，同时保持场所和行为不变。在该项目的下一阶段，我们将探索 时间单元如何组织组成特定情节的事件序列。此外，所有录制的 到目前为止，仅在CA1区检测到了海马区时间细胞。我们将考察时间是否 编码仅限于CA1，或广泛分布于海马体和其他内侧颞叶和前额叶区域。 我们还将探索时间序列是在海马体内部回路中产生的，还是 海马体内的时间编码依赖于来自皮质区域的输入。这些研究将对 流行的观点认为，海马体系统致力于空间导航和推动我们的 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.