Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461.
Department of Mathematics, Seattle University, Seattle, WA 98122.
eNeuro. 2020 Apr 23;7(2). doi: 10.1523/ENEURO.0244-19.2020. Print 2020 Mar/Apr.
In the auditory system, the spectrotemporal structure of acoustic signals determines the temporal pattern of spikes. Here, we investigated this effect in neurons of the barn owl's auditory midbrain () that are selective for auditory space and whether it can influence the coding of sound direction. We found that in the nucleus where neurons first become selective to combinations of sound localization cues, reproducibility of spike trains across repeated trials of identical sounds, a metric of across-trial temporal fidelity of spiking patterns evoked by a stimulus, was maximal at the sound direction that elicited the highest firing rate. We then tested the hypothesis that this stimulus-dependent patterning resulted in rate co-modulation of cells with similar frequency and spatial selectivity, driving stimulus-dependent synchrony of population responses. Tetrodes were used to simultaneously record multiple nearby units in the optic tectum (OT), where auditory space is topographically represented. While spiking of neurons in OT showed lower reproducibility across trials compared with upstream nuclei, spike-time synchrony between nearby OT neurons was highest for sounds at their preferred direction. A model of the midbrain circuit explained the relationship between stimulus-dependent reproducibility and synchrony, and demonstrated that this effect can improve the decoding of sound location from the OT output. Thus, stimulus-dependent spiking patterns in the auditory midbrain can have an effect on spatial coding. This study reports a functional connection between spike patterning elicited by spectrotemporal features of a sound and the coding of its location.
在听觉系统中，声音信号的时频结构决定了尖峰的时间模式。在这里，我们研究了对听觉空间具有选择性的仓鸮听觉中脑（）神经元中的这种效应，以及它是否能影响声音方向的编码。我们发现，在神经元首先对声音定位线索的组合变得具有选择性的核中，跨相同声音的重复试验重现尖峰序列的能力，即由刺激引发的尖峰模式的跨试验时间保真度的度量，在引发最高放电率的声音方向上最大。然后，我们测试了这样一个假设，即这种刺激依赖性模式导致具有相似频率和空间选择性的细胞的率共同调制，从而驱动群体反应的刺激依赖性同步。使用四极管同时记录光顶盖（OT）中多个附近的单元，听觉空间在那里呈地形表示。虽然与上游核相比，OT 中的神经元的尖峰在试验之间的重现性较低，但在其最佳方向的声音下，附近 OT 神经元之间的尖峰时间同步性最高。中脑电路的模型解释了刺激依赖性重现性和同步性之间的关系，并证明这种效应可以提高从 OT 输出解码声音位置的能力。因此，听觉中脑中刺激依赖性的尖峰模式可以对空间编码产生影响。本研究报告了声音的时频特征引发的尖峰模式与声音位置编码之间的功能联系。
