Department of Otolaryngology, Center for Hearing Research, University of California at Irvine, Irvine, CA, USA.
Cambridge Hearing Group, MRC Cognition and Brain Sciences Unit, University of Cambridge, Cambridge, UK.
J Assoc Res Otolaryngol. 2022 Aug;23(4):491-512. doi: 10.1007/s10162-022-00849-z. Epub 2022 Jun 6.
Cochlear implant (CI) users show limited sensitivity to the temporal pitch conveyed by electric stimulation, contributing to impaired perception of music and of speech in noise. Neurophysiological studies in cats suggest that this limitation is due, in part, to poor transmission of the temporal fine structure (TFS) by the brainstem pathways that are activated by electrical cochlear stimulation. It remains unknown, however, how that neural limit might influence perception in the same animal model. For that reason, we developed non-invasive psychophysical and electrophysiological measures of temporal (i.e., non-spectral) pitch processing in the cat. Normal-hearing (NH) cats were presented with acoustic pulse trains consisting of band-limited harmonic complexes that simulated CI stimulation of the basal cochlea while removing cochlear place-of-excitation cues. In the psychophysical procedure, trained cats detected changes from a base pulse rate to a higher pulse rate. In the scalp-recording procedure, the cortical-evoked acoustic change complex (ACC) and brainstem-generated frequency following response (FFR) were recorded simultaneously in sedated cats for pulse trains that alternated between the base and higher rates. The range of perceptual sensitivity to temporal pitch broadly resembled that of humans but was shifted to somewhat higher rates. The ACC largely paralleled these perceptual patterns, validating its use as an objective measure of temporal pitch sensitivity. The phase-locked FFR, in contrast, showed strong brainstem encoding for all tested pulse rates. These measures demonstrate the cat's perceptual sensitivity to pitch in the absence of cochlear-place cues and may be valuable for evaluating neural mechanisms of temporal pitch perception in the feline animal model of stimulation by a CI or novel auditory prostheses.
人工耳蜗（CI）使用者对电刺激传递的时间音高的敏感性有限，这导致他们对音乐和噪声中的语音感知受损。猫的神经生理学研究表明，这种限制部分是由于由电耳蜗刺激激活的脑干途径对时间精细结构（TFS）的传输不良。然而，尚不清楚这种神经限制如何影响同一动物模型中的感知。因此，我们开发了非侵入性的心理物理学和电生理学方法来测量猫的时间（即非频谱）音高处理。正常听力（NH）猫被呈现由带限谐波复音组成的声脉冲串，该声脉冲串模拟了基底耳蜗的 CI 刺激，同时去除了耳蜗位置兴奋的线索。在心理物理学程序中，受过训练的猫检测到从基础脉冲率到较高脉冲率的变化。在头皮记录程序中，在镇静猫中同时记录皮质诱发的声变化复合（ACC）和脑干产生的频率跟随反应（FFR），用于在基础和较高速率之间交替的脉冲串。对时间音高的感知灵敏度范围与人类大致相似，但略有提高。ACC 很大程度上与这些感知模式相吻合，验证了它作为时间音高敏感性的客观测量指标的用途。相比之下，锁相的 FFR 显示出对所有测试脉冲率的强烈脑干编码。这些测量方法证明了猫在没有耳蜗位置线索的情况下对音高的感知敏感性，并且可能对评估刺激的猫模型中的时间音高感知的神经机制有用，或者用于评估新型听觉假体。
