Department of Biomedical Engineering, Boston University Center for Computational Neuroscience and Neural Technology, Boston, MA 02215, USA.
Adv Exp Med Biol. 2013;787:501-10. doi: 10.1007/978-1-4614-1590-9_55.
We recently showed that listeners with normal hearing thresholds vary in their ability to direct spatial attention and that ability is related to the fidelity of temporal coding in the brainstem. Here, we recruited additional middle-aged listeners and extended our analysis of the brainstem response, measured using the frequency-following response (FFR). We found that even though age does not predict overall selective attention ability, middle-aged listeners are more susceptible to the detrimental effects of reverberant energy than young adults. We separated the overall FFR into orthogonal envelope and carrier components and used an existing model to predict which auditory channels drive each component. We find that responses in mid- to high-frequency auditory channels dominate envelope FFR, while lower-frequency channels dominate the carrier FFR. Importantly, we find that which component of the FFR predicts selective attention performance changes with age. We suggest that early aging degrades peripheral temporal coding in mid-to-high frequencies, interfering with the coding of envelope interaural time differences. We argue that, compared to young adults, middle-aged listeners, who do not have strong temporal envelope coding, have more trouble following a conversation in a reverberant room because they are forced to rely on fragile carrier ITDs that are susceptible to the degrading effects of reverberation.
我们最近发现，听力正常的听众在空间注意力定向能力方面存在差异，而这种能力与脑干中的时间编码保真度有关。在这里，我们招募了更多的中年听众，并扩展了我们对使用频率跟随反应（FFR）测量的脑干反应的分析。我们发现，尽管年龄并不能预测整体选择性注意能力，但中年听众比年轻人更容易受到混响能量的不利影响。我们将整体 FFR 分为正交包络和载波分量，并使用现有的模型来预测哪个听觉通道驱动每个分量。我们发现，从中等到高频听觉通道的响应主导包络 FFR，而较低频率的通道主导载波 FFR。重要的是，我们发现 FFR 的哪个分量预测选择性注意性能会随着年龄而变化。我们认为，早期衰老会降低中高频的外围时间编码，干扰包络的耳间时间差编码。我们认为，与年轻人相比，中年听众由于缺乏强烈的时间包络编码，因此在混响房间中更难以进行对话，因为他们被迫依赖容易受到混响影响的脆弱载波 ITD。
