Counting on inhibition and rate-dependent excitation in the auditory system
Counting on inhibition and rate-dependent excitation in the auditory system
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DOI：
10.1523/jneurosci.2816-07.2007
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发表时间：
2007-12-05
影响因子：
5.3
通讯作者：
Rose, Gary J.
中科院分区：
文献类型：
--
作者：
Edwards, Christofer J.;Leary, Christopher J.;Rose, Gary J.
声学元素之间的间隔在试听中很重要。尽管已记录到显示间隔调节的神经元，但其潜在机制尚不清楚。阿努拉听觉系统非常适合解决这个问题。无尾动物中的一类中脑神经元在较窄的脉冲重复率（PRR）范围内选择性地做出反应，并且仅在几个声音脉冲以“正确”的时间发生后才做出反应。这个“间隔计数”过程可以通过单个不正确的间隔来重置。在这里，我们通过体内中脑神经元的全细胞贴片记录表明，这些计算是抑制和速率依赖性兴奋之间相互作用的结果。单个脉冲或缓慢重复的脉冲引起抑制和阈下兴奋。然而，当 PRR 增加超过神经元特异性范围时，兴奋显着增强。当增强的兴奋克服了抑制时，就会产生尖峰。间隔数阈值与抑制强度和增强兴奋所需的间隔数呈正相关。因此，当通过用氟化铯负载细胞来减弱抑制作用时，间隔数阈值降低。这些神经元对脉冲间间隔的选择性以及因此的 PRR 与兴奋事件的时间进程和增强的速率依赖性有关。对于调整为较长间隔的细胞，EPSP 更宽，并且增强发生在较慢的 PRR 处。抑制的频率调谐通常跨越激励的频率调谐，与其在时间计算中的作用一致。这些发现提供了对神经系统中间隔选择性和计数的第一个机械理解。
The intervals between acoustic elements are important in audition. Although neurons have been recorded that show interval tuning, the underlying mechanisms are unclear. The anuran auditory system is well suited for addressing this problem. One class of midbrain neurons in anurans responds selectively over a narrow range of pulse-repetition rates (PRRs) and only after several sound pulses have occurred with the "correct" timing. This "interval-counting" process can be reset by a single incorrect interval. Here we show, from whole-cell patch recordings of midbrain neurons in vivo, that these computations result from interplay between inhibition and rate-dependent excitation. An individual pulse or slowly repeated pulses elicited inhibition and subthreshold excitation. Excitation was markedly enhanced, however, when PRR was increased over a neuron-specific range. Spikes were produced when the enhanced excitation overcame the inhibition. Interval-number thresholds were positively correlated with the strength of inhibition and number of intervals required to augment the excitation. Accordingly, interval-number thresholds decreased when inhibition was attenuated by loading cells with cesium fluoride. The selectivity of these neurons for the interpulse interval, and therefore PRR, was related to the time course of excitatory events and the rate dependence of enhancement; for cells that were tuned to longer intervals, EPSPs were broader, and enhancement occurred at slower PRRs. The frequency tuning of the inhibition generally spanned that of the excitation, consistent with its role in temporal computation. These findings provide the first mechanistic understanding of interval selectivity and counting in the nervous system.