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的言语感知能力都很强，而感觉神经性听力损失(SNHL)患者的言语感知能力通常要差得多。这些研究的长期目标是了解强健语音感知背后的神经信息和神经机制，以指导听觉假体新策略的发展，目前在不利条件下恢复正常语音感知特别困难。所提出的实验侧重于这样一种观点，即听觉神经(AN)时空反应模式中的非线性与耳蜗非线性调谐有关，并且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。如果是真的，这一结果将表明需要新的助听器策略，目前助听器不试图恢复AN中的正常时空模式。两个特定的目标集中在SNHL对AN和耳蜗核(CN)之间的增强的影响，这些增强发生在频谱和时间包络调制的编码中，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神经元对元音类刺激的反应来评估，其中重要的频谱特征移动到每个神经元的最佳频率附近。在安静和背景噪声中，反应都将作为水平的函数进行测量，以评估听力正常的猫和噪声性听力损失猫的稳健语音编码。将基于从测量的AN响应预测的简单交叉频率符合检测器的响应来评估增强语音编码的非线性时空响应模式的潜力。其次，SNHL对时间包络编码的稳健性的影响将通过量化目标1中收集的元音反应中的基频(F0)的时间和频谱表示来评估。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，这一结果将约束在CN中增强包络编码的可能的神经机制以及语音基音编码的知觉理论。听力受损的听众在复杂的声学环境中理解语音的困难可能部分是由于基于音调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.