Cortical Specializations for Behavioral Discrimination of Temporal Shape and Rhythm of Sound

人类语音和其他哺乳动物的发声在其幅度、形状和节奏上表现出广泛的变异性。这些声音特征允许区分并最终理解丰富的声音交流曲目，这些曲目表征了包括人类在内的各种动物的声音行为。本研究的重点是哺乳动物前脑上行听觉通路的不同阶段在分类和区分自然声音的时间变化中的作用，这是听觉生理学中的一个重要而悬而未决的问题。神经反应计时特性表明，次级腹侧听觉皮质允许更大范围的感觉时间处理，而初级听觉皮质没有考虑到这一点。将检查初级和次级听觉皮质的神经反应特性，以确定它们的功能组织和对感觉辨别行为的贡献。这种方法涉及到创造复杂的声音刺激，一方面是分析上容易处理的，另一方面是模仿自然声音的重要方面。神经反应将使用电生理、内在信号成像、行为和计算技术来表征。药物操作将允许进行可逆的功能丧失研究，以确定初级和次级听觉区域如何相互作用，以促进对声音中时间线索的行为辨别。此外，该项目将确定如何在神经和整个生物体水平上区分和编码声音中多个时间尺度上的时间线索，因为与其他通常用于听觉研究的哺乳动物相比，褐家鼠的初级听觉皮质和次级听觉皮质的表面积更大。这项研究的另一个目标是确定听觉前脑结构中通过并行和分级处理建立声音感知的程度。最后，将开发计算机模型，以确定神经活动模式的哪些方面对于区分交流声音的形状和节奏至关重要。这种多方面的方法应该允许对声音感知的前所未有的理解，这可能是广泛适用的。这项研究的结果将通过在科学会议上的陈述和同行评议的期刊文章来传播。

Human speech and other mammalian vocalizations exhibit extensive variability in their amplitude shape and rhythm. These sound features allow for discriminating and, ultimately, understanding the rich repertoire of vocal communications that characterize the vocal behavior of a large variety of animals including man. This proposal focuses on the roles of various stages of the mammalian forebrain ascending auditory pathway in categorizing and discriminating time variations in natural sounds, an important and open question in auditory physiology. Neural response timing properties suggest that secondary ventral auditory cortices allow for an extended range of sensory temporal processing not accounted for in primary auditory cortex. The neural response properties of primary and secondary auditory cortices will be examined to determine their functional organization and contribution to sensory discrimination behavior. The approach involves the creation of sophisticated acoustic stimuli that are analytically tractable on the one hand, while mimicking the important aspects of natural sounds on the other. Neural responses will be characterized using electrophysiological, intrinsic-signal imaging, behavioral and computational techniques. Pharmacological manipulations will allow reversible loss-of-function studies to determine how primary and secondary auditory areas interact to promote behavioral discrimination of temporal cues in sound. Further, this project will determine how temporal cues on multiple time scales in sound are discriminated and encoded on a neural and whole organism level for Rattus norvegicus, as this species has an expanded surface area for primary auditory cortex and secondary auditory cortex compared to other mammals commonly used in auditory studies. Another goal of the study is to determine the extent to which sound percepts are built up through parallel and hierarchal processing within auditory forebrain structures. Finally, computer models will be developed to determine what aspects of neural activity patterns are critical for discriminating between the shape and rhythm of communication sounds. This multifaceted approach should allow for an unprecedented understanding of vocal perception that could be broadly applicable. Results from the study will be disseminated through presentations at scientific meetings and through peer-reviewed journal articles.