Chrobak J J, Lörincz A, Buzsáki G
Department of Psychology, University of Connecticut, Storrs, USA.
Hippocampus. 2000;10(4):457-65. doi: 10.1002/1098-1063(2000)10:4<457::AID-HIPO12>3.0.CO;2-Z.
The anatomical connectivity and intrinsic properties of entorhinal cortical neurons give rise to ordered patterns of ensemble activity. How entorhinal ensembles form, interact, and accomplish emergent processes such as memory formation is not well-understood. We lack sufficient understanding of how neuronal ensembles in general can function transiently and distinctively from other neuronal ensembles. Ensemble interactions are bound, foremost, by anatomical connectivity and temporal constraints on neuronal discharge. We present an overview of the structure of neuronal interactions within the entorhinal cortex and the rest of the hippocampal formation. We wish to highlight two principle features of entorhinal-hippocampal interactions. First, large numbers of entorhinal neurons are organized into at least two distinct high-frequency population patterns: gamma (40-100 Hz) frequency volleys and ripple (140-200 Hz) frequency volleys. These patterns occur coincident with other well-defined electrophysiological patterns. Gamma frequency volleys are modulated by the theta cycle. Ripple frequency volleys occur on each sharp wave event. Second, these patterns occur dominantly in specific layers of the entorhinal cortex. Theta/gamma frequency volleys are the principle pattern observed in layers I-III, in the neurons that receive cortical inputs and project to the hippocampus. Ripple frequency volleys are the principle population pattern observed in layers V-VI, in the neurons that receive hippocampal output and project primarily to the neocortex. Further, we will highlight how these ensemble patterns organize interactions within distributed forebrain structures and support memory formation.
内嗅皮层神经元的解剖学连接性和内在特性产生了有序的群体活动模式。内嗅皮层群体如何形成、相互作用以及完成诸如记忆形成等涌现过程，目前还不太清楚。我们对神经元群体一般如何能与其他神经元群体不同地短暂发挥功能缺乏足够的了解。群体相互作用首先受到解剖学连接性和神经元放电的时间限制的约束。我们概述了内嗅皮层以及海马结构其他部分内神经元相互作用的结构。我们希望强调内嗅-海马相互作用的两个主要特征。首先，大量内嗅神经元被组织成至少两种不同的高频群体模式：伽马（40 - 100赫兹）频率阵发和涟漪（140 - 200赫兹）频率阵发。这些模式与其他明确的电生理模式同时出现。伽马频率阵发受θ节律调制。涟漪频率阵发在每个尖波事件时出现。其次，这些模式主要出现在内嗅皮层特定层中。θ/伽马频率阵发是在接收皮层输入并投射到海马的I - III层神经元中观察到的主要模式。涟漪频率阵发是在接收海马输出并主要投射到新皮层的V - VI层神经元中观察到的主要群体模式。此外，我们将强调这些群体模式如何组织分布式前脑结构内的相互作用并支持记忆形成。
