The Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, CA 95064.
Santa Cruz Institute for Particle Physics, University of California, Santa Cruz, CA 95064.
eNeuro. 2022 May 17;9(3). doi: 10.1523/ENEURO.0513-21.2022. Print 2022 May-Jun.
A topographic map of auditory space is a feature found in the superior colliculus (SC) of many species, including CBA/CaJ mice. In this genetic background, high-frequency monaural spectral cues and interaural level differences (ILDs) are used to compute spatial receptive fields (RFs) that form a topographic map along the azimuth. Unfortunately, C57BL/6 mice, a strain widely used for transgenic manipulation, display age-related hearing loss (AHL) because of an inbred mutation in the Cadherin 23 gene () that affects hair cell mechanotransduction. To overcome this problem, researchers have used young C57BL/6 mice in their studies, as they have been shown to have normal hearing thresholds. However, important details of the auditory response characteristics of the SC such as spectral responses and spatial localization, have not been characterized in young C57BL/6 mice. Here, we show that two- to four-month C57BL/6 mice lack neurons with frontal auditory RFs and therefore lack a topographic representation of auditory space in the SC. Analysis of the spectrotemporal RFs (STRFs) of the SC auditory neurons shows that C57BL/6 mouse SC neurons lack the ability to detect the high-frequency (>40 kHz) spectral cues that are needed to compute frontal RFs. We also show that crossing C57BL/6 mice with CBA/CaJ mice or introducing one copy of the wild-type to C57BL/6 mice rescues the high-frequency hearing deficit and improves the topographic map of auditory space. Taken together, these results demonstrate the importance of high-frequency hearing in computing a topographic map of auditory space.
听觉空间地形图是许多物种包括 CBA/CaJ 小鼠的上丘（SC）的一个特征。在这种遗传背景下，高频单耳频谱线索和两耳强度差（ILDs）被用来计算空间感受野（RFs），这些 RFs 沿着方位形成地形图。不幸的是，由于 Cadherin 23 基因（）的近交突变，广泛用于转基因操作的 C57BL/6 小鼠会出现年龄相关性听力损失（AHL），该突变会影响毛细胞的机械转导。为了克服这个问题，研究人员在研究中使用了年轻的 C57BL/6 小鼠，因为它们的听力阈值正常。然而，SC 的听觉反应特征的重要细节，如光谱反应和空间定位，在年轻的 C57BL/6 小鼠中尚未得到描述。在这里，我们表明，两到四个月大的 C57BL/6 小鼠缺乏具有额状听觉 RF 的神经元，因此缺乏 SC 中听觉空间的地形图表示。对 SC 听觉神经元的频谱时间 RF（STRFs）的分析表明，C57BL/6 小鼠 SC 神经元缺乏检测高频（>40 kHz）频谱线索的能力，而这些线索是计算额状 RF 所必需的。我们还表明，将 C57BL/6 小鼠与 CBA/CaJ 小鼠杂交，或向 C57BL/6 小鼠引入一个野生型等位基因，可挽救高频听力缺陷并改善听觉空间的地形图。总之，这些结果表明高频听力在计算听觉空间地形图中的重要性。
