School of Biological Sciences, Washington State University, 14204 NE Salmon Creek Ave., Vancouver, WA 98686, USA.
Neuroscience. 2011 Oct 13;193:429-39. doi: 10.1016/j.neuroscience.2011.07.025. Epub 2011 Jul 24.
Efficient encoding of sensory information can be implemented by heterogeneous response properties of neurons within sensory pathways. In the auditory system, neurons in the main auditory midbrain nucleus, the inferior colliculus (IC), show heterogeneous response properties to various types of acoustic stimuli including behaviorally relevant sounds. The receptive fields of these neurons, and their spatial organization, may reveal mechanisms that underlie response heterogeneity in the IC. The mouse is becoming an increasingly popular system for auditory studies and although some studies have examined spectral characteristics in the IC, most of these have been conducted in anesthetized animals. There were two goals of this study. The first goal was to examine the frequency representation of awake mouse IC in fine spatial resolution. The second goal was to determine whether there is a spatial organization of excitatory frequency tuning curves in the IC of awake mice. We achieved these goals by histologically reconstructing locations of single and multiunit recordings throughout the IC in a mouse strain with normal hearing (CBA/CaJ). We found that the tonotopic progression is discontinuous in mouse IC, and we found that there is no clear spatial organization of frequency tuning curve types. Rather, there is heterogeneity of receptive fields in the bulk of the IC such that frequency tuning characteristics and hence the structure of excitatory and inhibitory inputs does not depend on location in the IC. This heterogeneity likely provides a mechanism for efficient encoding of auditory stimuli throughout the extent of the mouse IC.
感觉信息的有效编码可以通过感觉通路中神经元的异质反应特性来实现。在听觉系统中，主要听觉中脑核团——下丘（inferior colliculus，IC）中的神经元对各种类型的声学刺激（包括与行为相关的声音）表现出异质的反应特性。这些神经元的感受野及其空间组织可能揭示了 IC 中反应异质性的基础机制。小鼠正成为听觉研究中越来越受欢迎的系统，尽管一些研究已经检查了 IC 中的光谱特征，但其中大多数是在麻醉动物中进行的。本研究有两个目标。第一个目标是在精细的空间分辨率下检查清醒小鼠 IC 的频率表示。第二个目标是确定在清醒小鼠的 IC 中是否存在兴奋性频率调谐曲线的空间组织。我们通过在具有正常听力的小鼠品系（CBA/CaJ）中对整个 IC 中的单个和多单位记录的位置进行组织学重建，实现了这些目标。我们发现，在小鼠 IC 中，音位的进展是不连续的，并且我们发现兴奋性调谐曲线类型没有明确的空间组织。相反，在 IC 的大部分区域存在感受野的异质性，使得频率调谐特性以及因此兴奋性和抑制性输入的结构不依赖于 IC 中的位置。这种异质性可能为整个小鼠 IC 中听觉刺激的有效编码提供了一种机制。
