SPEECH AND COMPLEX SIGNAL PROCESSING IN THE COCHLEAR NUCLEUS

本计画将以接近人类低频听阈的啮齿类动物龙猫为研究对象，利用平行的生理与心理物理学研究，探讨语音刺激如何呈现于腹侧耳蜗核。辅音，元音，并发元音和元音噪声损伤后的耳蜗的代表性将在三个主要的响应类别的单位，初级，开始和斩波器进行研究。声学信号的特定特征将在不同类别的单元的响应中被差分地表示。我们假设语音特征在耳蜗核水平的神经反应中被鲁棒地编码：单个细胞群将复杂频谱的不同频谱-时间特征传递到更高的中心：初级样神经元编码精细的频谱特征并保留时间-地点信息，斩波神经元对声门频率的共振峰和锁相等频谱特征进行速率编码;起始神经元既编码语音音高，又由于它们的快速适应而有助于某些语音的分段。不同单位类型的信号特征的同时表示是一个可能的结果。理想的观察者计算刺激将被用来量化之间的关系，单单位的活动和行为表现。结构/功能研究将在表征后采用单细胞标记，以将细胞形态与生理学和前腹侧耳蜗核的投射模式相关联。主要问题是球状/丛状细胞是否可以响应PL/N/PL/O/L模式，章鱼细胞是否可以响应O/I和O/L模式，以及是否存在C/S/C/T二分法的形态学相关性。对虚拟空间刺激的反应，同时用于听觉脑干和皮层的研究，也将被记录，以了解更多关于这些单位类别的差异功能的本地化意义的声音。

This project will study how speech stimuli are presented in the ventral cochlear nucleus using parallel physiological and psychophysical studies in a rodent with low frequency thresholds near that of humans, chinchilla laniger. The representation of consonants, vowels, concurrent vowels and vowels after noise damage of the cochlea will be studied in the three principal response categories of units, primary-like, onset and chopper. Particular features of the acoustic signal will be differentially represented in the responses of different classes of units. We hypothesize that phonetic features are robustly encoded in neural responses of units at the level of the cochlear nucleus: Individual cell groups covey different spectro-temporal features of complex spectra to higher centers: primary-like neurons code fine spectral features and preserve time-place information; chopper neurons rate code spectral features such as formants and phase lock to the glottal frequency; onset neurons both code voice pitch and the contribute to segmentation of some speech by virtue of their rapid adaptation. Simultaneous representation of signal features in different unit types is a possible outcome. Ideal observer computational stimulations will be used to quantify the relationship between single- unit activity and behavioral performance. Structure/function studies will employ single-cell labeling after characterization to correlate cell morphology with physiology and projection patterns from anteroventral cochlear nucleus. The main questions are whether globular/bushy cells can respond with PL/N/PL/O/L patterns, whether octopus cells can respond with both O/I and O/L patterns, and whether there is a morphological correlate of the C/S/C/T dichotomy. Responses to virtual-space stimuli, concurrently used for studies in the auditory brainstem and cortex, will also be recorded in order to learn more about the differential functions of these unit categories to sounds of localization significance.