Cellular diversity underlying timing- and intensity-based sound localization in the superior olivary complex

项目摘要 哺乳动物脑干中的上橄榄复合体(SOC)整合了来自两只耳朵的信息 定位声源并实现选择性听觉注意。外侧上橄榄(LSO)起关键作用 在这些职能中扮演的角色。外侧上橄榄核(LSO)的主神经元比较兴奋性输入 由同侧耳朵驱动，抑制输入由对侧耳朵驱动。LSO的胞格性质 PN是它们编码和传输信息的基础；然而，关键的细胞机制不是 但已经下定决心了。LSO的经典观点是它提取持续的耳间电平差异(ILDS)。近期 报告对这种想法提出了挑战，认为LSO的主要功能是对耳间时差进行编码 (ITDS)用于简短的声音或幅度调制。目前尚不清楚LSO是否主要在执行 然而，这些功能中的一项或两项都对LSO的细胞属性提出了不同的要求 神经元。此外，LSO PN之间存在细胞多样性，这一点尚未得到充分探索。我们最重要的是 假设存在适合ILD和ITD编码的LSO PN种群，并且它们的内在 属性、发射器系统和投影模式提供了一种在高等语言中组织这些信息的方法 中锋。该项目将对SOC的蜂窝组织产生基础性的见解，这可能是 在知之甚少的疾病状态下被破坏，如听觉处理障碍。 存在抑制性(I)和兴奋性(E)LSO PN，它们呈现不同的投射模式。在以下方面存在重大差距 我们所知道的是，这些I/E细胞类型之间的内在细胞差异还没有被研究过。我们会 利用已建立的报告鼠系，靶向I/E细胞进行体外实验。目标1将研究内在的 利用体外膜片钳和双光子成像技术构建I/E LSO PNS转基因脑片 报道小鼠、原位杂交、轨迹追踪和转录本方法。突触驱动与整合 LSO神经元的特性可以突出或抵消内在差异。在目标2中，我们将检查数字， 强度，以及突触输入到I/E细胞类型的短期动力学。基于生物物理学的计算 有助于系统研究ILD/ITD编码策略的突触差异和放电类型的模型 将补充我们的体外实验。信号如何在树突中传播是 神经元的整合功能。对LSO神经元的树突生理学几乎一无所知。在《目标3》中我们 将在靶向LSO神经元类型中使用双树突状/体细胞膜片钳技术来分析局部反应 以及与传播一起发生的信号变换。更高吞吐量的双光子钙成像 还将使用各种方法来评估信号传播。总之，这些实验将扩大我们对 LSO细胞类型的功能作用和完善的定位编码策略。这项建议在概念上是 创新地将LSO作为一个多样化的群体来处理，其细胞属性可针对多种功能角色进行调整 在转录学和树突状膜片钳的使用上，我们在方法上有所创新。

Project abstract The superior olivary complex (SOC) in the brainstem of mammals integrates information from the two ears to localize sound sources and enable selective auditory attention. The lateral superior olive (LSO) plays a critical role in these functions. Principal neurons (PNs) of the lateral superior olive (LSO) compare excitatory inputs driven by the ipsilateral ear with inhibitory inputs driven by the contralateral ear. The cellular properties of LSO PNs are fundamental to how they encode and transmit information; however, critical cellular mechanisms are not yet resolved. The classical view of the LSO is that it extracts ongoing interaural level differences (ILDs). Recent reports challenge this thinking, suggesting the major function of LSO is encoding interaural time differences (ITDs) for brief sounds or amplitude modulations. Currently it is not clear whether the LSO is primarily performing one of these functions or both, however, these roles place disparate demands on the cellular properties of LSO neurons. Furthermore, there is cellular diversity among LSO PNs that is not fully explored. Our overarching hypothesis is that there are LSO PN populations adapted for ILD and ITD coding and that their intrinsic properties, transmitter systems, and projection patterns provide a means to organize this information in higher centers. This project will yield foundational insights into the cellular organization of the SOC which may be disrupted in poorly understood disease states such as auditory processing disorder. There are inhibitory (I) and excitatory (E) LSO PNs that exhibit different projection patterns. A major gap in our knowledge is that intrinsic cellular differences between these I/E cell types has not been examined. We will target I/E cells for ex vivo experiments using established reporter mouse lines. Aim 1 will examine the intrinsic properties of I/E LSO PNs using ex vivo patch-clamp and two-photon imaging in brain slices from transgenic reporter mice, in situ hybridization, tract tracing, and transcriptomic approaches. Synaptic drive and integrative properties of LSO neurons could accentuate or offset intrinsic differences. In Aim 2 we will examine the number, strength, and short-term dynamics of synaptic inputs onto I/E cell types. Biophysically-based computational models that facilitate the systematic study of synaptic differences and firing types on ILD/ITD coding strategies will complement our ex vivo experiments. How signals propagate in dendrites is a critical component of integrative functions in neurons. Almost nothing is known of the dendritic physiology of LSO neurons. In Aim 3 we will use dual dendritic/somatic patch-clamp technique in targeted LSO neuron types to analyze local responses as well as signal transformations that occur with propagation. Higher throughput two-photon calcium imaging methods will also be used to assess signal propagation. Together these experiments will expand our view of the functional role of LSO cell types and sound localization coding strategies. This proposal is conceptually innovative in its treatment of the LSO as a diverse group with cellular properties tuned for multiple functional roles and methodologically innovative in our use of transcriptomics and dendritic patch-clamp.