Romani Sandro, Tsodyks Misha
Department of Neurobiology, Weizmann Institute of Science, Rehovot 76100, Israel; Department of Neuroscience, Center for Theoretical Neuroscience, College of Physicians and Surgeons, Columbia University, New York, New York; Department of Neuroinformatics, Donders Centre for Neuroscience, Radboud University, 6525, Nijmegen, The Netherlands.
Hippocampus. 2015 Jan;25(1):94-105. doi: 10.1002/hipo.22355. Epub 2014 Sep 25.
Rodent hippocampus exhibits strikingly different regimes of population activity in different behavioral states. During locomotion, hippocampal activity oscillates at theta frequency (5-12 Hz) and cells fire at specific locations in the environment, the place fields. As the animal runs through a place field, spikes are emitted at progressively earlier phases of the theta cycles. During immobility, hippocampus exhibits sharp irregular bursts of activity, with occasional rapid orderly activation of place cells expressing a possible trajectory of the animal. The mechanisms underlying this rich repertoire of dynamics are still unclear. We developed a novel recurrent network model that accounts for the observed phenomena. We assume that the network stores a map of the environment in its recurrent connections, which are endowed with short-term synaptic depression. We show that the network dynamics exhibits two different regimes that are similar to the experimentally observed population activity states in the hippocampus. The operating regime can be solely controlled by external inputs. Our results suggest that short-term synaptic plasticity is a potential mechanism contributing to shape the population activity in hippocampus.
啮齿动物的海马体在不同行为状态下表现出截然不同的群体活动模式。在运动过程中，海马体活动以θ频率（5 - 12赫兹）振荡，细胞在环境中的特定位置（即位置场）放电。当动物跑过一个位置场时，在θ周期的逐渐提前阶段会发放尖峰信号。在静止状态下，海马体表现出尖锐的不规则活动爆发，偶尔会有位置细胞的快速有序激活，这表达了动物可能的轨迹。这种丰富多样的动力学背后的机制仍不清楚。我们开发了一种新颖的循环网络模型来解释所观察到的现象。我们假设该网络在其循环连接中存储了环境地图，这些连接具有短期突触抑制。我们表明，网络动力学表现出两种不同的模式，类似于在海马体中实验观察到的群体活动状态。其运行模式可以仅由外部输入控制。我们的结果表明，短期突触可塑性是塑造海马体群体活动的一种潜在机制。
