Department of Neuroscience, Johns Hopkins University, Baltimore, Maryland 21205, USA.
J Comp Neurol. 2013 May 1;521(7):1510-32. doi: 10.1002/cne.23238.
The relationship between structure and function is an invaluable context with which to explore biological mechanisms of normal and dysfunctional hearing. The systematic and topographic representation of frequency originates at the cochlea, and is retained throughout much of the central auditory system. The cochlear nucleus (CN), which initiates all ascending auditory pathways, represents an essential link for understanding frequency organization. A model of the CN that maps frequency representation in 3D would facilitate investigations of possible frequency specializations and pathologic changes that disturb frequency organization. Toward this goal, we reconstructed in 3D the trajectories of labeled auditory nerve (AN) fibers following multiunit recordings and dye injections in the anteroventral CN of the CBA/J mouse. We observed that each injection produced a continuous sheet of labeled AN fibers. Individual cases were normalized to a template using 3D alignment procedures that revealed a systematic and tonotopic arrangement of AN fibers in each subdivision with a clear indication of isofrequency laminae. The combined dataset was used to mathematically derive a 3D quantitative map of frequency organization throughout the entire volume of the CN. This model, available online (http://3D.ryugolab.com/), can serve as a tool for quantitatively testing hypotheses concerning frequency and location in the CN.
结构与功能之间的关系是探索正常和功能障碍听力的生物学机制的宝贵背景。频率的系统和拓扑表示起源于耳蜗，并在大部分中枢听觉系统中得以保留。耳蜗核（CN）是所有上行听觉通路的起始点，它是理解频率组织的重要环节。一个能够以 3D 形式映射频率表示的 CN 模型将有助于研究可能干扰频率组织的频率专门化和病理变化。为了实现这一目标，我们在 CBA/J 小鼠的前腹侧 CN 中进行了多单位记录和染料注射，重建了标记听神经（AN）纤维的 3D 轨迹。我们观察到每次注射都会产生连续的标记 AN 纤维片。使用 3D 对齐程序将个别病例归一化为模板，揭示了每个细分中的 AN 纤维具有系统的和音调的排列，并有明确的等频层指示。将合并后的数据集用于从整个 CN 体积中数学推导频率组织的 3D 定量图。该模型可在线获取（http://3D.ryugolab.com/），可作为定量测试有关 CN 中频率和位置的假设的工具。
