SPEECH AND COMPLEX SIGNAL PROCESSING IN THE COCHLEAR NUCLEUS

该项目将在一种低频阈值与人类相近的啮齿类动物--栗鼠身上，采用平行的生理学和心理物理学研究，研究语言刺激是如何在耳蜗腹核内呈现的。声母、元音、同时元音和元音在噪声损伤后的耳蜗声母、元音和元音的表征将在三个主要的单位反应类别中进行研究，即初级类、首发和斩波。声学信号的特定特征将在不同类别的单元的响应中不同地表示。我们假设，语音特征在耳蜗核水平的单位的神经反应中被强健地编码：单个细胞群将复杂频谱的不同谱特征覆盖到更高的中枢：初级类神经元编码精细的频谱特征并保留时间-地点信息；斩波神经元对共振峰和相位锁定等声门频率的编码频谱特征进行速率编码；起始神经元通过其快速适应来编码语音音调和对某些语音的分割做出贡献。不同单元类型的信号特征的同时表示是一种可能的结果。理想的观察者计算刺激将被用来量化单一单位活动和行为表现之间的关系。结构/功能研究将在表征后使用单细胞标记，以将细胞形态与生理和来自耳蜗前腹侧核的投射模式相关联。主要问题是球状/丛状细胞是否能以PL/N/PL/O/L模式反应，章鱼细胞是否能同时以O/I和O/L模式反应，以及是否存在C/S/C/T二分法的形态相关性。对虚拟空间刺激的反应，同时用于听觉脑干和皮质的研究，也将被记录下来，以便更多地了解这些单位类别对具有本地化意义的声音的不同功能。

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.