Thalamocortical Circuits and Auditory Neocortical Maps

描述（由申请人提供）：听力和言语理解的基础在于首先在基底膜水平看到的频率图。这张地图在整个提升听觉系统中被保存，直到并包括听觉新皮层。虽然听觉脑干中的结构适应是已知的，但对于听觉丘脑和AI中这些地图的解剖学基础知之甚少。最近，我们证实了存在两个功能不同的区域在兔MGV; pars lateralis（LV）和pars ovoidea（OV）。与其他物种相比，这些地区可以很容易区分免疫细胞化学和解剖学的兔子，使这个物种的听觉神经系统的结构/功能关系的研究的一个很好的模型。用常规尼氏染色法可以看到兔MGV中的层状结构。绘图研究表明，纹层是MGV频率图的基础。层内的MGV神经元的焦点组以斑片状或簇状的方式投射到AI。结合解剖学和电生理学研究表明，这些丘脑板似乎支配不同的功能区编码频率和双耳在听觉皮层。这些数据支持存在多个不同的通道连接听觉丘脑和新皮层。我们已经开发了一个模型，该模型解释了来自LV的斑块状TC投影如何解释不连续（例如，双耳性），以及连续的（例如，频率），AI中的地图。将在麻醉的NZW家兔中使用顺行标记和电生理方法的组合测试该模型。在具体目标1中，将使用顺行标记和电生理标测的组合来比较从OV和LV投射到AI的神经回路。在特定目标2中，将使用双顺行标记和标测研究来确定不同的椎板如何投射到AI并有助于皮质标测。在具体目标3中，我们将应用与具体目标2相似的技术，比较单个LV板中两个生理学不同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中功能地图的结构基础，并对理解正常，衰老和受损人耳的听觉皮层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.