A second function of gamma frequency oscillations: an E%-max winner-take-all mechanism selects which cells fire.
A second function of gamma frequency oscillations: an E%-max winner-take-all mechanism selects which cells fire.
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DOI：
10.1523/jneurosci.6044-08.2009
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发表时间：
2009-06-10
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影响因子：
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通讯作者：
Lisman JE
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文献类型：
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作者：
de Almeida L;Idiart M;Lisman JE
伽马振荡在产生主细胞群的同步放电中的作用是众所周知的。在这里，我们认为伽马振荡还有第二个功能：它们选择激发哪些主细胞。这种选择过程通过激励和伽马频率反馈抑制的相互作用发生。我们试图了解管理这一过程的规则。一种可能性是，恒定比例的细胞会被点燃。然而，我们的分析表明，这一比例并不稳健，因为它取决于激发到不同细胞的分布。一种稳健的描述称为E%-max：如果细胞在具有最大激发的细胞的E%内具有阈值上的激发(E)，则细胞被激发。反馈抑制延迟与膜时间常数之比可近似表示E%-max的值。根据实测值，我们估计E%-max为5-15%。因此，E%-max赢家通吃的过程可以区分在激发方面只有很小差异的细胞组。为了测试这个框架的实用性，我们分析了V1中振荡的作用，V1是少数几个直接测量尖峰和细胞内兴奋的系统之一。我们发现，E%-max赢家通吃过程提供了一个简单的解释，为什么激发的定向调谐比激发输入的定向调谐更窄，为什么这种差异不受激发的增加的影响。由于伽马振荡发生在大脑的许多区域，我们为理解伽马的第二功能而开发的框架可能具有广泛的适用性。
The role of gamma oscillations in producing synchronized firing of groups of principal cells is well known. Here we argue that gamma oscillations have a second function: they select which principal cells fire. This selection process occurs through the interaction of excitation with gamma frequency feedback inhibition. We sought to understand the rules that govern this process. One possibility is that a constant fraction of cells fire. Our analysis shows, however, that the fraction is not robust because it depends on the distribution of excitation to different cells. A robust description is termed E%-max: cells fire if they have suprathreshold excitation (E) within E% of the cell that has maximum excitation. The value of E%-max is approximated by the ratio of the delay of feedback inhibition to the membrane time-constant. From measured values, we estimate that E%-max is 5–15%. Thus, an E%-max winner-take-all process can discriminate between groups of cells that have only small differences in excitation. To test the utility of this framework, we analyzed the role of oscillations in V1, one of the few systems where both spiking and intracellular excitation have been directly measured. We show that an E%-max winner-take-all process provides a simple explanation for why the orientation tuning of firing is narrower than that of the excitatory input and why this difference is not affected by increasing excitation. Because gamma oscillations occur in many brain regions, the framework we have developed for understanding the second function of gamma is likely to have wide applicability.