In vivo contribution of neurons of the intermediate nucleus of the lateral lemniscus for sound processing.

外侧丘系中间核(INLL)是外侧丘系的三个核之一，负责处理和传递耳蜗核、上橄榄复合体和听觉中脑之间的听觉信息。虽然另外两个丘脑核团的功能至少部分已被了解，但INLL在声音处理中的参与在很大程度上是未知的。此外，INLL神经元的递质类型似乎具有物种特异性，因为啮齿类动物和蝙蝠分别被标记为谷氨酸和甘氨酸能标记。从动物模型的听力远低于和高于2千赫，如人类，几乎没有任何功能数据从这个听觉脑干结构可用。目前INLL的解剖和功能数据表明，它可能参与了不同频率之间的听觉信息整合。这种跨频整合是产生我们听觉环境的神经元表征的关键过程。为了阐明INLL的过滤功能和功能作用，我们建议用在体单单位电生理学的方法来研究这一听觉结构的声音处理特征。最初，我们将记录由一系列声音刺激引起的听觉反应，范围从纯音到同种叫声。这种刺激电池使我们能够描述INLL神经元的基本处理特征。下一步，我们将确定INLL神经元的时间和频率依赖的积分特性。我们初步的活体单单元记录通过分析受刺激的转置音调的调制传递函数来突出时间滤波功能。与来自BAT的现有数据一致，我们发现了不同声音频率之间声音整合的证据。对滤波函数和集成特性的深入了解将使我们能够假设INLL在声音处理中的功能角色。最后，我们计划进行全细胞活体记录，以获得INLL神经元如何完成其处理任务的机械性见解。因此，这项应用将阐明听觉脑干结构的功能作用，这种结构连接良好，但很难被理解，因此，该提议将大大增加我们对声音处理的理解，以及我们如何在大脑中生成听觉世界。

The intermediate nuclei of the lateral lemniscus (INLL) is one of the three nuclei of the lateral lemniscus that process and relay auditory information between the cochlear nucleus, the superior olivary complex and the auditory midbrain. While the function of the other two lemniscal nuclei is at least partially understood the involvement of the INLL in sound processing is largely unknown. Moreover, the transmitter type of INLL neurons seem species specific, as rodents and bats are labelled for glutamatergic and glycinergic markers respectively. From animal models that hear well below and above 2 kHz, like humans, hardly any functional data from this auditory brainstem structure is available. The present anatomical and functional data of the INLL indicates that it might be involved in the integration of auditory information between different frequencies. Such a cross-frequency integration is key process for generating the neuronal representation of our auditory environment. To elucidate the filter functions and functional role of the INLL we propose to investigate the sound processing features of this auditory structure with in vivo single unit electrophysiology. Initially, we will record acoustically evoked responses elicited by a battery of sound stimulations ranging from pure tones to conspecific calls. This stimulation battery allows us to characterize the basic processing features of INLL neurons. In the next step, we will determine the temporal and frequency dependent integration characteristics of INLL neurons. Our preliminary in vivo single unit recordings highlight the temporal filter functions by analyzing modulation transfer functions of stimulated transposed tones. In agreement with existing data from bat, we find evidence for integration of sounds between different sound frequencies. Obtaining deeper insights into the filter functions and integration characteristics will allow us to postulate functional roles of the INLL in sound processing. Finally, we plan to perform whole-cell in vivo recordings to gain mechanistic insight how INLL neurons achieve their processing tasks. Thus, this application will illuminate the functional role of an auditory brainstem structure that is well connected but hardly understood and therefore the proposal will substantially add to our understanding of sound processing and how we generate our auditory world in our brain.