Auditory Processing in Songbirds

听觉经验对于歌曲学习是必不可少的，在某些物种中，对于维持正常的成年歌曲模式是必不可少的。控制歌曲学习、感知和产生的脑核团的连接和功能已经得到了广泛的研究。这些细胞核被统称为鸣唱系统。在鸣唱系统中，听觉神经元对鸟类自己的歌声表现出特殊的敏感性。这种特殊的听觉调节是在鸟学习唱歌的过程中发展起来的。歌曲系统从听觉系统接收其主要的感觉输入，但对听觉系统如何处理发声知之甚少。我的长期目标是描述鸣禽听觉系统中用于交流的发声处理的特征，并研究这种处理在歌曲学习和维持中的作用。这项研究将探讨鸣禽听觉中脑区域（中脑外侧部背侧部）对自然声音和合成声音的处理。这个脑区是哺乳动物下丘（IC）的鸟类同源物，在蝙蝠和小鼠中发现了对同种发声的专门反应。第一组实验将表征Mld神经元的光谱时间调谐。表征将直接使用常规方法（即通过表征神经元的频率调谐曲线、幅度调制和频率调制响应）和间接地通过首先估计具有复杂合成刺激的神经元的频谱时间感受野（STRF），然后从STRF提取神经元的调谐参数来完成。我们的第二个具体目标是评估谱-时间特征是否完全描述了Mld神经元的响应特性，或者更高阶的结构（例如在自然声音中发现的结构）是否也会影响它们的响应。第三个目标将开始解决同种发声的听觉调谐问题。我们将描述两种鸣禽，斑胸草雀和孟加拉雀，同种和异种发声MLd神经元的反应。这些实验将测试Mld神经元是否专门提取同种声音信号的声学特征。两者合计，实验的目的是提供第一次检查的声音通信相关的听觉处理鸣禽中脑。

Auditory experience is essential for song learning and, in some species, for the maintenance of normal adult song patterns. The connectivity and functioning of brain nuclei controlling song learning, perception and production have been extensively examined. Together, these nuclei are called the song system. In the song system, auditory neurons show specialized sensitivity to the bird's own song. This specialized auditory tuning develops as the bird is learning to produce its song. The song system receives its primary sensory input from the auditory system, yet very little is known about how vocalizations are processed by the auditory system. My long-term goal is to characterize the processing of vocalizations used for communication in the songbird auditory system and to examine the role of this processing in song learning and maintenance. The proposed research will examine the processing of natural and synthetic sounds in the songbird auditory midbrain region, the mesencephalicus lateralis, pars dorsalis (MLd). This brain region is the avian homologue of the mammalian inferior colliculus (IC), where specialized responses to conspecific vocalizations are found in bats and mice. The first set of experiments will characterize the spectral temporal tuning of Mld neurons. Characterizations will be done both directly using conventional methods (Le by characterizing a neuron's frequency tuning curves, amplitude modulation and frequency modulation responses) and indirectly by first estimating the spectral temporal receptive fields (STRFs) of neurons with complex synthetic stimuli and then extracting the tuning parameters of the neurons from the STRF. Our second Specific Aim is to assess whether the spectral-temporal characteristics completely describe the response properties on Mld neurons or whether higher order structure (such as that found in natural sound) can also affect their responses. The third Aim will begin to address the issue of auditory tuning for conspecific vocalizations. We will characterize the responses of MLd neurons in two species of songbird, zebra finches and bengalese finches, to conspecific and heterospecific vocalizations. These experiments will test whether or not Mld neurons are specialized to extract the acoustic features of conspecific vocal signals. Taken together, the experiments are designed to provide the first examination of auditory processing related to vocal communication in the songbird midbrain.