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

外侧丘系中间核（intermediate nucleus of the lateral lemniscus，INLL）是外侧丘系的三个核团之一，在耳蜗核、上级橄榄复合体和听觉中脑之间处理和传递听觉信息。虽然其他两个丘系核的功能至少部分了解，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种属特异性，因为啮齿动物和蝙蝠分别标记有谷氨酸能和甘氨酸能标记物。从动物模型，听到低于和高于2 kHz，像人类，几乎没有任何功能数据，从这个听觉脑干结构。现有的INLL的解剖和功能数据表明，它可能参与不同频率之间的听觉信息的整合。这种跨频率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研究这个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诱发反应，从纯音到同种呼叫。这种刺激电池使我们能够表征INLL神经元的基本处理功能。在下一步中，我们将确定INLL神经元的时间和频率依赖性整合特性。我们的初步在体内单单位录音突出的时间滤波器功能，通过分析调制传递函数的刺激转置音。在协议与现有的数据蝙蝠，我们发现的证据整合不同的声音频率之间的声音。获得更深入的了解过滤器功能和集成特性将使我们能够假设的功能作用的INLL在声音处理。最后，我们计划进行全细胞体内记录，以获得INLL神经元如何实现其处理任务的机制。因此，该应用程序将阐明听觉脑干结构的功能作用，该结构连接良好但几乎不被理解，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.