ONTOGENY OF THE SPATIAL CODING OF SOUND FREQUENCY

最近有人假设， 频率沿着耳蜗在发育过程中发生变化。 这一假设 预测了听觉中枢内的音调组织 在个体发育过程中， 为了验证这一点， 鸟类脑干听觉核团的组织mangocellularis和 n. laminaris在胚胎和出生后发育期间被绘制。 这些实验是这些研究的继续和延伸。 在前两个实验中，电生理标测程序将 用于（1）在17天内完成音调组织的映射 胚胎，和（2）映射的tonotopic组织在最早的阶段 功能发展。 这些研究的完成将提供 全定量描述的发展tonotopic 组织，机构巨细胞群和大细胞群。椎板。 第三 辣根过氧化物酶示踪神经元 连接将用于确定 基底乳头（耳蜗）和神经。大细胞变化 发展 这将决定音调的变化是否 已经观察到的组织可以通过重新映射来解释 基底乳头与神经的连接。大细胞的 频率空间编码变化的功能后果 沿着耳蜗的是，在发育过程中， 将最大限度地激活神经元的不同亚群， 听核 这可能对理解 早期声环境如何影响听觉系统发育。 频率的空间编码的变化也可能具有重要的影响。 临床意义 如果耳蜗沿着放置 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，或因各种条件而发生变化， 听力障碍和听觉系统功能障碍。 这些可能性 需要在今后的研究中加以研究。

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.