Developmental Studies of Sound Localization Mechanisms

描述（由申请人提供）：本项目的目标是了解声源位置和编码它们的神经回路的声学线索的同步发展。定位的所有线索都可以在头部相关方向传递函数（DTFs）的测量中捕获，其包含三个主要线索，耳间时间差（ITD）和水平差（ILD）以及单耳频谱形状线索。由于这些线索的形成是由头部和脊椎的线性尺寸决定的，因此线索的相对大小将随着这些结构的生长而变化。这些实验测试的假设，在发展的线索之一，ILD，有一个伴随发展的能力，在外侧上级橄榄（LSO），双耳互动的最外围网站之一，编码ILD的细胞。目的我将测试的假设，线索将改变的方式，从头部和脊椎的尺寸增加可预测的。将在1周龄至成年的小猫中测量DTF，并从中提取位置线索。这些线索将与头部和脊椎的测量结果进行比较。目标II将检验以下假设：LSO细胞编码的ILD范围将在发育期间随着目标I中测量的物理ILD幅度的预期增加而增加。此外，将研究向LSO提供对侧抑制输入的斜方体内侧核中的细胞对ILD计算所需的复杂光谱形状进行编码的能力。这些研究将确定这些在上升双耳系统中的核团是否以及在多长时间内可以补偿头部和耳廓声学特性的发育变化所带来的线索变化。最后，目标III将研究的正常机制，通过该线索的位置，特别是那些基于频谱形状（ILD和单耳频谱线索），编码的LSO及其传入成年猫。目标二和目标二1将使用若干技术，包括虚拟空间模拟和系统识别方法。我们假设，在整个人口的输入到LSO，复杂的频谱形状表示和LSO计算的频谱差异提取ILD从这些输入。更好地理解复杂的声音频谱是如何表现的，将有助于更好地设计听觉假体（如人工耳蜗和助听器）的处理策略。

DESCRIPTION (provided by applicant): The goals of this project are to understand the concurrent development of the acoustical cues to sound source location and the neural circuits that encode them. All cues for localization can be captured in measurements of head related directional transfer functions (DTFs), which contain the three main cues, interaural differences in time (ITDs) and level (ILDs) and monaural spectral shape cues. Since the formation of these cues is governed by the linear dimensions of the head and pinnae, the relative magnitudes of the cues will change as these structures grow. These experiments test the hypothesis that during the development of one of the cues, ILD, there is a concomitant development of the ability of cells in the lateral superior olive (LSO), one of the most peripheral sites for binaural interaction, to encode ILDs. Aim I will test the hypothesis that the cues will change in ways predictable from the increasing dimensions of the head and pinnae. DTFs will be measured in kittens aged from 1 week to adult and the cues to location extracted from them. The cues will be compared to measurements of the head and pinnae. Aim II will test the hypothesis that the range of ILDs encoded by LSO cells will increase during development with the expected increase in the magnitudes of the physical ILDs, as measured in Aim I. Also, the ability of cells in the medial nucleus of the trapezoid body, which provide the contralateral inhibitory input to the LSO, to encode the complex spectral shapes necessary for ILD computation will be studied. These studies will determine if and how long these nuclei in the ascending binaural system can compensate for changes in the cues brought about by developmental changes in the acoustical properties of the head and pinnae. Finally, Aim III will study the normal mechanisms by which the cues to location, in particular those based on spectral shape (ILDs and monaural spectral cues), are encoded by the LSO and its afferents in adult cats. Several techniques, including virtual space stimulation and a systems identification method, will be used in Aims II and II1. We hypothesize that across a population of inputs to the LSO, complex spectral shape is represented and that the LSO computes a spectral difference to extract the ILD from these inputs. A better understanding of how complex sound spectra are represented will lead to better designs for the processing strategies in auditory prosthetics like cochlear implants and hearing aids.