Bharadwaj Hari M, Masud Salwa, Mehraei Golbarg, Verhulst Sarah, Shinn-Cunningham Barbara G
Center for Computational Neuroscience and Neural Technology and Department of Biomedical Engineering, Boston University, Boston, Massachusetts 02215,
Center for Computational Neuroscience and Neural Technology and Department of Biomedical Engineering, Boston University, Boston, Massachusetts 02215.
J Neurosci. 2015 Feb 4;35(5):2161-72. doi: 10.1523/JNEUROSCI.3915-14.2015.
Clinical audiometry has long focused on determining the detection thresholds for pure tones, which depend on intact cochlear mechanics and hair cell function. Yet many listeners with normal hearing thresholds complain of communication difficulties, and the causes for such problems are not well understood. Here, we explore whether normal-hearing listeners exhibit such suprathreshold deficits, affecting the fidelity with which subcortical areas encode the temporal structure of clearly audible sound. Using an array of measures, we evaluated a cohort of young adults with thresholds in the normal range to assess both cochlear mechanical function and temporal coding of suprathreshold sounds. Listeners differed widely in both electrophysiological and behavioral measures of temporal coding fidelity. These measures correlated significantly with each other. Conversely, these differences were unrelated to the modest variation in otoacoustic emissions, cochlear tuning, or the residual differences in hearing threshold present in our cohort. Electroencephalography revealed that listeners with poor subcortical encoding had poor cortical sensitivity to changes in interaural time differences, which are critical for localizing sound sources and analyzing complex scenes. These listeners also performed poorly when asked to direct selective attention to one of two competing speech streams, a task that mimics the challenges of many everyday listening environments. Together with previous animal and computational models, our results suggest that hidden hearing deficits, likely originating at the level of the cochlear nerve, are part of "normal hearing."
长期以来，临床听力测定一直专注于确定纯音的检测阈值，该阈值取决于完整的耳蜗力学和毛细胞功能。然而，许多听力阈值正常的听众抱怨存在沟通困难，而此类问题的原因尚不清楚。在此，我们探讨听力正常的听众是否存在此类阈上缺陷，这些缺陷会影响皮层下区域对清晰可听声音的时间结构进行编码的保真度。我们使用一系列测量方法，对一群听力阈值在正常范围内的年轻人进行评估，以同时评估耳蜗的机械功能和阈上声音的时间编码。听众在时间编码保真度的电生理和行为测量方面差异很大。这些测量结果之间存在显著相关性。相反，这些差异与耳声发射、耳蜗调谐的适度变化或我们研究群体中存在的听力阈值残余差异无关。脑电图显示，皮层下编码能力较差的听众对耳间时间差异变化的皮层敏感性较差，而耳间时间差异对于声源定位和分析复杂场景至关重要。当被要求将选择性注意力指向两个相互竞争的语音流之一时，这些听众的表现也很差，这一任务模拟了许多日常听力环境中的挑战。结合之前的动物和计算模型，我们的结果表明，可能起源于耳蜗神经水平的隐性听力缺陷是“正常听力”的一部分。
