Encoding of vocal Signals in the Auditory System

描述（由申请人提供）：本研究的中心目标是了解脊椎动物的听觉系统如何能够识别和解释大量物种典型的声音交流信号。声音交流并不是人类独有的，而是许多非哺乳动物脊椎动物共有的特征。这里的重点是声音制作！会发声的硬骨鱼提供了模型系统来识别导致包括人类在内的哺乳动物复杂听觉系统进化的神经操作的基本原理。会发声的硬骨鱼有一系列简单的物种典型信号，这些信号对它们的社会和繁殖行为至关重要。这些信号很容易复制，个体对自然或计算机合成信号的回放产生刻板的行为反应。硬骨鱼也有类似陆生脊椎动物（包括哺乳动物）的中枢听觉系统。我们认为，平鳍中船鱼（Porichthys notatus）具有发声和声学行为，以及潜在的神经编码机制和电路，这些都是解决所有脊椎动物面临的声学问题所必需和充分的。尤其是海军军官候补生鱼，它们发出的广告和激动的叫声具有高度不同的身体特征。雄性用持续时间很长的嗡嗡声（秒-1小时）向雌性求爱，并表现出由低基频（90-100赫兹）和几个谐波组成的基本平坦的包络。相比之下，雄性也会发出包络调制的激动信号，即以2-3赫兹的间隔发出短暂（50-200毫秒）的咕噜声（咕噜声有像嗡嗡声一样的FOs）。包络调制也被引入，当两个雄性的嗡嗡声重叠，产生一个小的不同频率（0-8赫兹）的声拍，由两个FOs的差异决定。行为研究表明，海军军官候补生根据信号的持续时间、信号之间的无声间隔和包络调制的程度来区分嗡嗡声和非嗡嗡声（节拍和咕噜声脉冲序列）。三个具体目标将探讨听觉机制如何为蜂群和非蜂群的行为分类提供神经基础。目的1使用生理测量（尖峰率和同步）和模拟自然发声的刺激来研究脑干编码机制，以将声音信号分类为嗡嗡声或非嗡嗡声。目的2将把这些神经生理学测量与细胞外和细胞内染料标记相结合，以描绘目的1中鉴定的神经元的功能电路。目的3将研究季节性，生殖状态依赖的可塑性负责外周和中枢听觉系统的差异处理。

DESCRIPTION (provided by applicant): The central goal of the research proposed here is to understand how the vertebrate auditory system is able to recognize and interpret an enormous repertoire of species-typical vocal communication signa's. Sound communication is not unique to humans, but rather is a trait shared with many non-mammalian vertebrates. The focus here is on sound producing! vocalizing teleost fish that provide model systems to identify the basic principles of neural operation that have lead to the evolution of the complex auditory system of mammals, including humans. Vocalizing teleosts have a simple repertoire of species-typical signals central to their social and reproductive behavior. These signals can be easily reproduced and individuals produce stereotyped behavioral responses to playbacks of natural or computer-synthesized signals. Teleosts also have a central auditory system resembling that of terrestrial vertebrates including mammals. We propose that the plainfin midshipman fish (Porichthys notatus) has the vocal and acoustic behaviors, and underlying neural encoding mechanisms and circuitry, both necessary and sufficient to solve acoustic problems that challenge all vertebrates. Midshipman fish, in particular, produce advertisement and agonistic vocalizations with highly divergent physical attributes. Males acoustically court females using hums that are long duration (secs-l h) and exhibit an essentially flat envelope consisting of a low fundamental frequency (90-100 Hz) and several harmonics. In contrast, males also emit agonistic signal with envelope modulations, namely brief (50-200 ms) grunts at intervals of 2-3 Hz (grunts have FOs like hums). Envelope modulations are also introduced when the hums of two males overlap to produce an acoustic beat with a small difference frequency (0-8 Hz) determined by the difference in the two FOs. Behavioral studies show that individual midshipman distinguish hums from non-hums (beats and grunt-hke pulse trains) based on signal duration, silent gaps between signals and the degree of envelope modulation. Three specific aims will investigate how auditory mechanisms provide a neural basis for the behavioral categorization of hums from non-hums. Aim 1 uses physiological measures (spike rate and synchronization) and stimuli that mimic natural vocalizations to investigate brainstem encoding mechanisms for categorizing acoustic signals as either hums or non-hums. Aim 2 will couple these neurophysiological measures with extracellular and intracellular dye labeling to delineate the functional circuitry of the neurons identified in Aim 1. Aim 3 will investigate seasonal, reproductive state-dependent plasticity responsible for differential processing in the peripheral and central auditory systems.