RIKEN Center for Brain Science and RIKEN Brain Science Institute, Wako-shi, Saitama, Japan.
Toho University, Funabashi-shi, Chiba, Japan.
PLoS Comput Biol. 2020 Nov 6;16(11):e1007726. doi: 10.1371/journal.pcbi.1007726. eCollection 2020 Nov.
Neurons in various regions of the brain generate spike bursts. While the number of spikes within a burst has been shown to carry information, information coding by interspike intervals (ISIs) is less well understood. In particular, a burst with k spikes has k-1 intraburst ISIs, and these k-1 ISIs could theoretically encode k-1 independent values. In this study, we demonstrate that such combinatorial coding occurs for retinal bursts. By recording ganglion cell spikes from isolated salamander retinae, we found that intraburst ISIs encode oscillatory light sequences that are much faster than the light intensity modulation encoded by the number of spikes. When a burst has three spikes, the two intraburst ISIs combinatorially encode the amplitude and phase of the oscillatory sequence. Analysis of trial-to-trial variability suggested that intraburst ISIs are regulated by two independent mechanisms responding to orthogonal oscillatory components, one of which is common to bursts with a different number of spikes. Therefore, the retina encodes multiple stimulus features by exploiting all degrees of freedom of burst spike patterns, i.e., the spike number and multiple intraburst ISIs.
大脑不同区域的神经元会产生爆发式尖峰。虽然爆发式尖峰的数量已经被证明可以携带信息，但尖峰之间的间隔（interspike intervals，ISIs）的信息编码方式还不太清楚。特别是，一个有 k 个尖峰的爆发式尖峰有 k-1 个爆发内 ISIs，这 k-1 个爆发内 ISIs 理论上可以编码 k-1 个独立的值。在这项研究中，我们证明了视网膜爆发式尖峰存在这种组合编码。通过记录来自孤立蝾螈视网膜的神经节细胞尖峰，我们发现爆发内 ISIs 编码的光序列比由尖峰数量编码的光强度调制快得多。当一个爆发有三个尖峰时，两个爆发内 ISIs 以组合的方式编码了振荡序列的幅度和相位。对试验间变异性的分析表明，爆发内 ISIs 受到两种独立机制的调节，它们分别对两个正交的振荡分量做出反应，其中一个机制对具有不同尖峰数量的爆发都有反应。因此，视网膜通过利用爆发式尖峰模式的所有自由度，即尖峰数量和多个爆发内 ISIs，来编码多个刺激特征。
