Traub R D, Whittington M A, Stanford I M, Jefferys J G
IBM Research Division, T. J. Watson Research Center, Yorktown Heights, New York 10598, USA.
Nature. 1996 Oct 17;383(6601):621-4. doi: 10.1038/383621a0.
Synchronous neuronal oscillations in the 30-70 Hz range, known as gamma oscillations, occur in the cortex of many species. This synchronization can occur over large distances, and in some cases over multiple cortical areas and in both hemispheres; it has been proposed to underlie the binding of several features into a single perceptual entity. The mechanism by which coherent oscillations are generated remains unclear, because they often show zero or near-zero phase lags over long distances, whereas much greater phase lags would be expected from the slow speed of axonal conduction. We have previously shown that interneuron networks alone can generate gamma oscillations; here we propose a simple model to explain how an interconnected chain of such networks can generate coherent oscillations. The model incorporates known properties of excitatory pyramidal cells and inhibitory interneurons; it predicts that when excitation of interneurons reaches a level sufficient to induce pairs of spikes in rapid succession (spike doublets), the network will generate gamma oscillations that are synchronized on a millisecond time-scale from one end of the chain to the other. We show that in rat hippocampal slices interneurons do indeed fire spike doublets under conditions in which gamma oscillations are synchronized over several millimetres, whereas they fire single spikes under other conditions. Thus, known properties of neurons and local synaptic circuits can account for tightly synchronized oscillations in large neuronal ensembles.
30 - 70赫兹范围内的同步神经元振荡，即所谓的伽马振荡，在许多物种的皮层中都会出现。这种同步可以在很长距离上发生，在某些情况下，会跨越多个皮层区域以及两个半球；有人提出，它是将多个特征绑定为单个感知实体的基础。相干振荡产生的机制仍不清楚，因为它们在长距离上通常显示零或接近零的相位滞后，而从轴突传导的缓慢速度来看，预期会有大得多的相位滞后。我们之前已经表明，仅中间神经元网络就能产生伽马振荡；在此，我们提出一个简单模型来解释这样的网络相互连接的链如何产生相干振荡。该模型纳入了兴奋性锥体细胞和抑制性中间神经元的已知特性；它预测，当中间神经元的兴奋达到足以诱导快速连续出现成对尖峰（尖峰 doublet）的水平时，网络将产生在毫秒时间尺度上从链的一端到另一端同步的伽马振荡。我们表明，在大鼠海马切片中，中间神经元在伽马振荡在几毫米范围内同步的条件下确实会发放尖峰 doublet，而在其他条件下则发放单个尖峰。因此，神经元和局部突触回路的已知特性可以解释大型神经元群体中紧密同步的振荡。
