Effects of sensorineural loss on robust speech coding

描述（由申请人提供）：听力正常的听者在各种情况下都有很强的言语感知能力，而感觉神经性听力损失（SNHL）的人通常表现出更弱的言语感知能力。这些研究的长期目标是了解稳健语音感知背后的神经信息和神经机制，以指导听觉假体的新策略的发展，目前听觉假体在不利条件下难以恢复正常的语音感知。这些实验的重点是，听觉神经（AN）时空响应模式的非线性，与非线性耳蜗调谐有关，由生理上脆弱的外毛细胞产生，可能有助于稳健的语音编码。如果这是真的，这一结果将表明需要新的助听器策略，目前还没有尝试恢复正常的AN时空模式。两个特定的目标集中在SNHL对AN和耳蜗核（CN）之间的频谱和时间包络调制编码增强的影响，这是语音信号的两个重要特性。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响应来评估，这些元音样刺激的重要频谱特征在每个神经元的最佳频率附近移动。在安静和背景噪音下，将测量反应水平的函数，以评估听力正常的猫和噪音导致听力损失的猫的稳健语音编码。非线性时空响应模式增强语音编码的潜力将基于从测量的AN响应预测的简单交叉频率重合检测器的响应来评估。其次，SNHL对时间包络编码鲁棒性的影响将通过量化Aim 1中收集的元音响应的基频（F0）的时间和频谱表示来评估。如果SNHL在ann和CN中对F0的周期性和时间-地点测量有不同的影响，这一结果将限制CN中增强包络编码的可能神经机制以及音高编码的感知理论。听力受损的听众在复杂的声学环境中理解语音的困难，部分原因可能是他们根据音高区分声源的能力下降。

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.