ONTOGENY OF THE SPATIAL CODING OF SOUND FREQUENCY

最近有一种假设认为， 在发育过程中，沿耳蜗线的频率会发生变化。这一假设 预测中央听觉内的音调组织 在个体发育过程中，途径应该发生转变。为了测试这一点，托洛托普 鸟类脑干听觉核团芒果细胞核团的组织 在胚胎和出生后的发育过程中，已经绘制了N.laminaris的图谱。 拟议的实验是这些研究的延续和延伸。 在前两个实验中，电生理标测程序将 用于(1)在17天内完成主题组织的测绘 胚胎，以及(2)绘制最早阶段的紧张性组织图 关于功能发展的。这些研究的完成将提供一个 全程定量描述直立位的发展 巨细胞亚种和片层亚种的组织结构。在第三节 辣根过氧化物酶技术追踪神经的实验研究 连接将被用来确定 基底乳头(耳蜗体)和巨细胞核团的变化 发展。这将决定色调是否发生变化 已经观察到的组织可以通过重新映射 基底乳头与大细胞核之间的联系。 频率的空间编码改变的功能结果 沿着耳蜗线的是在发育过程中相同的声刺激 将最大限度地激活不同神经元亚群 听觉核团。这可能会对理解 早期的声学环境如何影响听觉系统的发育。 频率的空间编码的改变也可能具有重要的 临床意义。如果耳蜗线上的位置之间的关系 而频率不一定是固定的，那么这种关系也可能 在老化过程中发生变化，或因各种情况而发生变化 听力障碍和听觉系统功能障碍。这些可能性 需要在未来的研究中进行检查。

It has recently been hypothesized that the spatial representation of frequency along the cochlea changes during development. This hypothesis predicts that the tonotopic organization within the central auditory pathway should shift during ontogeny. To test this, the tonotopic organization of the avian brain stem auditory nuclei n. mangocellularis and n. laminaris has been mapped during embryonic and postnatal development. The proposed experiments are a continuation and extension of these studies. In the first two experiments electrophysiological mapping procedures will be used to (1) complete the mapping of tonotopic organization in the 17 day embryo, and (2) map the tonotopic organization during the earliest stages of functional development. The completion of these studies will provide a complete quantitative description of the development of tonotopic organization in n. magnocellularis and n. laminaris. In the third experiment the horseradish peroxidase technique for tracing neural connections will be used to determine if the projections between the basilar papilla (cochlea) and n. magnocellularis change during development. This will determine whether the changes in tonotopic organization which have been observed can be explained by a remapping of connections between the basilar papilla and n. magnocellularis. The functional consequence of a change in the spatial encoding of frequency along the cochlea is that during development the same acoustic stimulus will maximally activate different subpopulations of neurons within an auditory nucleus. This may have important implications for understanding how the early acoustic environment influences auditory system development. A change in the spatial encoding of frequency may also have important clinical implications. If the relationship between place along the cochlea and frequency is not necessarily fixed, then this relationship might also change during aging or be altered by various conditions that result in hearing impairment and auditory system dysfunction. These possibilities need to be examined in future studies.