Our sense of hearing enables the processing of stimuli that differ in sound pressure by more than six orders of magnitude. How to process a wide range of stimulus intensities with temporal precision is an enigmatic phenomenon of the auditory system. Downstream of dynamic range compression by active cochlear micromechanics, the inner hair cells (IHCs) cover the full intensity range of sound input. Yet, the firing rate in each of their postsynaptic spiral ganglion neurons (SGNs) encodes only a fraction of it. As a population, spiral ganglion neurons with their respective individual coding fractions cover the entire audible range. How such “dynamic range fractionation” arises is a topic of current research and the focus of this review. Here, we discuss mechanisms for generating the diverse functional properties of SGNs and formulate testable hypotheses. We postulate that an interplay of synaptic heterogeneity, molecularly distinct subtypes of SGNs, and efferent modulation serves the neural decomposition of sound information and thus contributes to a population code for sound intensity.

中文翻译：

---

多样性很重要——内毛细胞通过异质突触扩展声音强度编码

我们的听觉能够处理声压相差六个数量级以上的刺激。如何以时间精度处理各种刺激强度是听觉系统的一个神秘现象。在主动耳蜗微机械动态范围压缩的下游，内毛细胞 (IHC) 覆盖声音输入的整个强度范围。然而，每个突触后螺旋神经节神经元（SGN）的放电率只编码其中的一小部分。作为一个群体，螺旋神经节神经元及其各自的编码部分覆盖了整个听觉范围。这种“动态范围分级”是如何产生的，是当前研究的一个主题，也是本综述的重点。在这里，我们讨论了生成 SGN 多种功能特性的机制，并提出了可检验的假设。我们假设突触异质性、SGN 分子上不同的亚型和传出调制之间的相互作用服务于声音信息的神经分解，从而有助于形成声音强度的群体代码。