Department of Biomedical Engineering, Center for Computational Neuroscience and Neural Technology, Boston University, Boston, MA 02215, USA.
Curr Biol. 2012 Aug 7;22(15):1417-22. doi: 10.1016/j.cub.2012.05.025. Epub 2012 Jun 21.
Anecdotally, middle-aged listeners report difficulty conversing in social settings, even when they have normal audiometric thresholds [1-3]. Moreover, young adult listeners with "normal" hearing vary in their ability to selectively attend to speech amid similar streams of speech. Ignoring age, these individual differences correlate with physiological differences in temporal coding precision present in the auditory brainstem, suggesting that the fidelity of encoding of suprathreshold sound helps explain individual differences [4]. Here, we revisit the conundrum of whether early aging influences an individual's ability to communicate in everyday settings. Although absolute selective attention ability is not predicted by age, reverberant energy interferes more with selective attention as age increases. Breaking the brainstem response down into components corresponding to coding of stimulus fine structure and envelope, we find that age alters which brainstem component predicts performance. Specifically, middle-aged listeners appear to rely heavily on temporal fine structure, which is more disrupted by reverberant energy than temporal envelope structure is. In contrast, the fidelity of envelope cues predicts performance in younger adults. These results hint that temporal envelope cues influence spatial hearing in reverberant settings more than is commonly appreciated and help explain why middle-aged listeners have particular difficulty communicating in daily life.
据传闻，中年听众在社交场合中交谈困难，即使他们的听力阈值正常[1-3]。此外，听力“正常”的年轻成年听众在类似的语音流中选择性地关注语音的能力存在差异。忽略年龄因素，这些个体差异与听觉脑干中存在的时间编码精度的生理差异相关，这表明超阈声音的编码保真度有助于解释个体差异[4]。在这里，我们重新探讨了早期衰老是否会影响个体在日常环境中交流能力的难题。尽管绝对选择性注意力能力不受年龄影响，但随着年龄的增长，混响能量对选择性注意力的干扰更大。我们将脑干反应分解为对应于刺激精细结构和包络编码的成分，发现年龄改变了哪个脑干成分可以预测表现。具体来说，中年听众似乎严重依赖于时间精细结构，而混响能量对时间精细结构的干扰比时间包络结构更大。相比之下，包络线索的保真度可以预测年轻成年人的表现。这些结果表明，时间包络线索在混响环境中对空间听觉的影响比人们通常认为的要大，这有助于解释为什么中年听众在日常生活中特别难以交流。
