Phase precession of grid cells in a network model without external pacemaker
Phase precession of grid cells in a network model without external pacemaker
复制标题
无外部起搏器的网络模型中网格单元的相位进动
DOI：
10.1002/hipo.22133
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发表时间：
2013
期刊：
影响因子：
3.5
通讯作者：
Leibold C
中科院分区：
文献类型：
--
作者：
Thurley K;Hellmundt F;Leibold C
啮齿类动物的大脑编码空间的放电率和尖峰时间的神经元在内侧内嗅皮层。速率编码是通过网格场实现的，即神经元在排列在六边形晶格上的多个地方放电。这种活动伴随着局部场电位的θ振荡。尖峰脉冲的相位也会对空间进行编码，因为它会随着在磁场中行进的距离而减小，这种现象称为相位进动。网格细胞的一个可能的候选者是内嗅皮层星状细胞，它是II型振荡器，并被认为是起起搏器作用。目前尚不清楚这种假定的起搏神经元的尖峰如何能够相对于自发振荡在相位上进行进动。本文提出了一个计算模型，如何解决这个悖论，虽然网格字段的周期性干扰的神经元的周期性放电。我们的模拟结果表明，星状细胞之间的连接同步小细胞群，这使得人口振荡网格场活动，伴随着θ相位进动。星状细胞之间的直接兴奋性耦合，通过中间神经元的γ振荡网络的间接抑制性耦合，或两者都可以介导这种相位协调。我们的模型进一步表明，h电流的调制是一种可行的机制，可以将相位进动调整到运行速度。因此，空间的速率码和时间码的共存是循环网络自组织的自然结果。© 2013威利期刊公司.
Rodent brains encode space in both the firing rate and the spike timing of neurons in the medial entorhinal cortex. The rate code is realized by grid fields, that is, the neurons fire at multiple places that are arranged on a hexagonal lattice. Such activity is accompanied by theta oscillations of the local field potential. The phase of spikes thereby encodes space as well, since it decreases with the distance traveled in the field—a phenomenon called phase precession. A likely candidate for grid cells are entorhinal cortex stellate cells, which are type II oscillators and have been suggested to act as pacemakers. It is unclear how spiking of such putative pacemaker neurons would be able to precess in phase relative to a self‐generated oscillation. This article presents a computational model of how this paradox can be resolved although the periodicity of the grid fields interferes with the periodic firing of the neurons. Our simulations show that the connections between stellate cells synchronize small cell groups, which allows a population oscillation during grid field activity that is accompanied by theta phase precession. Direct excitatory coupling between the stellate cells, indirect inhibitory coupling via a gamma‐oscillating network of interneurons, or both could mediate this phase coordination. Our model further suggests modulation of h‐currents to be a feasible mechanism to adjust phase precession to running‐speed. The coexistence of rate and timing code for space hence follows as a natural consequence of the self‐organization in a recurrent network. © 2013 Wiley Periodicals, Inc.
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