Developmental Studies of Sound Localization Mechanisms

描述（由申请人提供）：这个项目的目标是了解声源位置的声音线索和编码它们的神经回路的同步发展。所有定位线索都可以在头部相关定向传递函数（dtf）的测量中捕获，它包含三个主要线索，即耳间时间差异（ITDs）和水平差异（ILDs）以及单耳光谱形状线索。由于这些线索的形成是由头部和耳廓的线性尺寸决定的，因此线索的相对大小将随着这些结构的增长而变化。这些实验验证了这样一种假设，即在其中一种信号（ILD）的发展过程中，双耳相互作用的最外围部位之一——侧上橄榄（LSO）的细胞编码ILD的能力也随之发展。目的：我将测试一个假设，即线索会以可预测的方式改变，从头部和耳廓的尺寸增加。研究人员将测量从1周龄到成年的小猫的dtf，并从中提取位置线索。这些球杆将与头部和耳廓的尺寸进行比较。Aim II将验证一个假设，即LSO细胞编码的ILDs范围将在发育过程中随着物理ILDs的预期增加而增加，正如Aim i中所测量的那样。此外，将研究梯形体内侧核中的细胞（为LSO提供对侧抑制输入）编码ILD计算所需的复杂光谱形状的能力。这些研究将确定上升双耳系统中的这些核是否以及在多长时间内可以补偿由头部和耳廓声学特性的发育变化所带来的线索变化。最后，Aim III将研究成年猫的LSO及其传入信号编码的正常机制，特别是那些基于光谱形状的线索（ILDs和单耳光谱线索）。一些技术，包括虚拟空间刺激和系统识别方法，将在目标II和II1中使用。我们假设，在输入到LSO的总体中，复杂的光谱形状被表示出来，并且LSO计算光谱差以从这些输入中提取ILD。更好地理解复杂的声谱是如何表示的，将有助于更好地设计像人工耳蜗和助听器这样的听觉假肢的处理策略。

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.