RUI: Processing of Complex Sounds in the Auditory Midbrain

人类听觉系统的一个基本功能是处理语言。其他动物的说话和群居发声都很复杂，因为它们由许多随时间变化的频率元素组成。当这些声音第一次被内耳的耳蜗编码时，它们被分解成单独的频率元素，单个神经元对单个频率元素做出反应。然而，为了能够感知整个声音，听觉系统中的神经元必须以适当的时间顺序重新组合单个频率元素。换句话说，单个神经元必须随着时间的推移整合多个频率元素。在上升听觉系统中，单个神经元在复杂声音的频率元素中整合的第一个位置是下丘（IC）。本研究的目的是确定频率和时间整合在IC中编码复杂声音中的作用。在本项目中，将获得IC中单个神经元对频谱和时间复杂声音（包括自然发声）的反应。该项目的重点是描述神经元对两种不同频带能量的声音组合的非线性相互作用的反应。然后，该项目研究了这些“组合敏感”神经元如何通过呈现自然的老鼠发声来编码自然的声音。将比较整个发声、单个频率元素和具有不同时间关系的元素组合所引起的神经反应。经过验证的假设是，小鼠IC中的神经元对含有适当时间顺序的生物学上重要的频率元素的信号表现出非线性频率相互作用，并且这些组合敏感的相互作用是编码自然发声的机制。该建议的优势在于利用清醒小鼠模型中自然发生的生物相关发声来研究复杂声音处理背后的神经机制。由于小鼠发声与人类语音的元音结构相似，并且小鼠和人类对多谐波通信呼叫的感知存在相似性，因此该项目将是确定语音处理神经机制的重要一步。该项目的研究活动的影响超出了科学发现。波特斯博士在教育学生和社区方面建立了多元化和坚定的记录。这些活动包括通过研究机会吸引少数民族学生，通过整合研究和教学活动吸引本科生，以及通过教师培训研讨会、公开讲座和当地媒体吸引当地社区成员。波特斯博士经常在实验室和课堂之外从事许多对社区有广泛影响的活动。在典型的一年里，她和她的学生要向学校和社区团体做10到20次演讲。该项目将继续促进本科生和研究生在实验室的互动，并通过听觉神经科学的演讲向社区提供推广。

A fundamental function of the auditory system in humans is to process speech. Both speech sounds and social vocalizations of other animals are complex in that they are comprised of many frequency elements that vary over time. When these sounds are first encoded by the cochlea in the inner ear, they are broken down into their individual frequency elements and single neurons respond to individual frequency elements. However, to enable perception of the whole sound, neurons in the auditory system must recombine the individual frequency elements in theappropriate temporal order. In other words, individual neurons must integrate multiple frequency elements over time. The first site in the ascending auditory system where individual neurons integrate across frequency elements in complex sounds is the inferior colliculus (IC). The objective of this research is to determine the role of frequency and temporal integration in encoding complex sounds in the IC. In this project, responses of individual neurons in the IC to spectrally and temporally complex sounds, including natural vocalizations, will be obtained. The project focuses on characterizing neuronal responses that display nonlinear interactions to thecombination of two sounds with energy in different frequency bands. The project then examines how these "combination-sensitive" neurons encode natural sounds by presenting natural mouse vocalizations. Neural responses elicited by the entire vocalization, individual frequency elements and combinations of elements with different temporal relationships will be compared. The hypothesis tested is that neurons in the mouse IC show nonlinear frequency interactions to signals that contain biologically important frequency elements in the appropriate temporal order, and that these combination-sensitive interactions are a mechanism for encoding naturalvocalizations. The strength of this proposal is in utilizing naturally occurring, biologically relevant vocalizations in an awake mouse model to study neural mechanisms underlying the processing of complex sounds. Because mouse vocalizations have similar structures to the vowels of human speech, and similarities exist between the perception of multi-harmonic communication calls in mice and humans, this project will be an important step towards identifying the neural mechanisms of speech processing. The research activities in this project have an impact beyond the scientific findings. Dr. Portfors has established a diverse and committed record of educating students and the community. These activities include engaging minority students through research opportunities, undergraduate students through integration of research and teaching activities, and members of the local community through teacher training workshops, public lectures, and the local media. Dr. Portfors is regularly engaged in numerous activities outside the laboratory and classroom that have broad impact on the community. In a typical year, she and her students give 10-20 presentations to schools and community groups. This project will continue to foster interaction of undergraduate and graduate students in the laboratory and provide outreach to the community through presentations on auditory neuroscience.