Effects of sensorineural loss on robust speech coding

描述（由申请人提供）：听力正常的听众的语音感知在各种条件下都是稳健的，而感觉神经性听力损失（SNHL）的人通常表现出不太稳健的语音感知。这些研究的长期目标是了解神经信息和神经机制的基础上强大的语音感知，以指导开发新的策略，听觉假体，目前有特别困难的恢复正常的语音感知在不利的条件下。拟议的实验集中在的想法，非线性神经（AN）的时空响应模式，这是与非线性耳蜗调谐和产生的生理脆弱的外毛细胞，可能有助于强大的语音编码。如果是真的，这一结果将表明需要新的策略，助听器，目前不试图恢复正常的时空模式在AN。两个具体的目标集中在SNHL的增强发生在AN和耳蜗核（CN）之间的编码的频谱和时间包络调制，语音信号的两个重要属性的影响。首先，频谱编码将通过测量AN纤维和CN神经元对元音样刺激的反应来评估，其中重要的频谱特征在每个神经元的最佳频率附近移动。将在安静和背景噪声中测量响应作为水平的函数，以评价听力正常猫和噪声诱导听力损失猫的稳健语音编码。非线性时空响应模式，以提高语音编码的潜力将进行评估的基础上预测从测量的AN响应的一个简单的交叉频率重合检测器的响应。第二，SNHL的时间包络编码的鲁棒性的影响将通过量化的时间和频谱表示的基本频率（F0）从目标1中收集的元音响应进行评估。如果在AN和CN中观察到SNHL对F0的周期性和时间位置测量的不同影响，则该结果将限制CN中增强包络编码的潜在神经机制以及语音音高编码的感知理论。听力受损的听众在复杂声学环境中理解语音的困难可能部分是由于基于语音音高分离声源的能力降低。

DESCRIPTION (provided by applicant): Speech perception by listeners with normal hearing is robust across a wide variety of conditions, whereas people with sensorineural hearing loss (SNHL) typically show much less robust speech perception. The long term goal of these studies is to understand the neural information and neural mechanisms that underlie robust speech perception in order to guide the development of novel strategies for auditory prostheses, which currently have particular difficulty restoring normal speech perception in adverse conditions. The proposed experiments focus on the idea that nonlinearities in auditory-nerve (AN) spatio-temporal response patterns, which are associated with nonlinear cochlear tuning and are produced by the physiologically vulnerable outer hair cells, may contribute to robust speech coding. If true, this result would suggest the need for novel strategies for hearing aids, which currently do not attempt to restore normal spatio-temporal patterns in the AN. Two specific aims focus on the effects of SNHL on enhancements that occur between the AN and cochlear nucleus (CN) in the coding of both spectral and temporal-envelope modulations, two important properties of speech signals. First, spectral coding will be evaluated by measuring the responses of AN fibers and CN neurons to vowel-like stimuli with important spectral features shifted near the best frequency of each neuron. Responses will be measured as a function of level, both in quiet and in background noise, to evaluate robust speech coding in cats with normal hearing and in cats with a noise induced hearing loss. The potential for nonlinear spatio-temporal response patterns to enhance speech coding will be evaluated based on responses of a simple cross-frequency coincidence detector predicted from measured AN responses. Second, the effects of SNHL on the robustness of temporal-envelope coding will be evaluated by quantifying temporal and spectral representations of the fundamental frequency (F0) from the vowel responses collected in Aim 1. If different effects of SNHL on periodicity and temporal-place measures of F0 were observed in the AN and CN, this result would constrain the possible neural mechanisms underlying enhanced envelope coding in the CN as well as perceptual theories of voice-pitch coding. The difficulty hearing-impaired listeners have in understanding speech in complex acoustic environments may be due in part to a reduced ability to segregate sound sources based on voice pitch.