Thalamocortical Circuits and Auditory Neocortical Maps

描述(申请人提供)：听力和言语理解的基础是在基底膜水平上第一次看到的频率图。这张图被保存在整个上升的听觉系统中，直到并包括听觉新皮质。虽然频率图背后的听觉脑干的结构适应是已知的，但对于听觉丘脑和人工智能中这些图的解剖基础了解很少。最近，我们证实了兔MGV中存在两个功能不同的区域：外侧侧部(LV)和卵形部(OV)。与其他物种相比，兔的这些区域可以很容易地在免疫细胞化学和解剖学上区分开来，使该物种成为研究听觉神经系统结构/功能关系的极佳模型。常规尼氏染色可见兔MGV的层状结构。作图研究表明，MGV频率图下有薄层。板层内MGV神经元的焦点群以斑块或簇状的方式向AI投射。解剖和电生理相结合的研究表明，这些丘脑板似乎支配着听觉皮质中不同的功能区，编码频率和双耳。这些数据支持存在连接听觉丘脑和新皮质的多个分叉通道。我们已经开发了一个模型，解释了来自左室的斑块TC投影如何解释人工智能中不连续(例如，双耳)以及连续(例如，频率)的映射。这一模型将在麻醉的新西兰兔身上使用顺行标记和电生理方法相结合的方法进行测试。在具体目标1中，将使用顺行标记和电生理标测相结合的方法来比较从OV和LV投射到AI的神经回路。在具体目标2中，将使用双顺行标记和标测研究来确定不同的板层如何投射到AI并对皮层映射做出贡献。在特定目标3中，我们将应用与特定目标2中类似的技术来比较单个LV椎板中两个不同生理位置的丘脑皮质投射模式和功能地形图。这些研究有可能揭示人工智能功能图的结构基础，并对理解正常、衰老和受损的人耳的听觉皮质可塑性具有重要意义。

DESCRIPTION (provided by applicant): The basis of hearing and speech comprehension lies in the frequency map first seen at the level of the basilar membrane. This map is preserved throughout the ascending auditory system up to and including the auditory neocortex. Although the structural adaptations in the auditory brainstem that underlie frequency maps are known, very little is understood regarding the anatomical substrate for these maps in the auditory thalamus and AI. Recently, we confirmed the existence of two functionally distinct regions in the rabbit MGV; the pars lateralis (LV) and pars ovoidea (OV). In contrast to other species, these regions can be easily distinguished immunocytochemically and anatomically in the rabbit, making this species an excellent model for studying structural/functional relationships in the auditory nervous system. A laminar architecture in the rabbit MGV is visible with routine Nissl stains. Mapping studies have revealed that the laminae underlie the MGV frequency map. Focal groups of MGV neurons within a laminae project in a patchy or clustered manner to AI. Combined anatomical and electrophysiological studies indicate that these thalamic laminae appear to innervate separate functional regions coding frequency and binaurality in the auditory cortex. These data support the existence of multiple divergent channels linking the auditory thalamus and neocortex. We have developed a model that explains how patchy TC projections from the LV can account for discontinuous (e.g., binaurality), as well as continuous (e.g., frequency), maps in AI. This model will be tested using a combination of anterograde labeling and electrophysiological methods in anesthetized NZW rabbits. In specific aim 1, a combination of anterograde labeling and electrophysiological mapping will be used to compare the neural circuits that project from the OV and LV to AI. In specific aim 2, double anterograde labeling and mapping studies will be used to determine how different laminae project to AI and contribute to cortical maps. In specific aim 3, we will apply techniques similar to those in specific aim 2 to compare thalamocortical projection patterns and functional topography from two physiologically distinct locations in a single LV lamina. These studies have the potential for revealing the structural basis of functional maps in AI and have important implications for understanding auditory cortical plasticity in normal, aging and impaired human ears.