Many older listeners have difficulty understanding speech in noise, when cues to speech-sound identity are less redundant. The amplitude envelope of speech fluctuates dramatically over time, and features such as the rate of amplitude change at onsets (attack) and offsets (decay) signal critical information about the identity of speech sounds. Aging is also thought to be accompanied by increases in cortical excitability, which may differentially alter sensitivity to envelope dynamics. Here, we recorded electroencephalography in younger and older human adults (of both sexes) to investigate how aging affects neural synchronization to 4-Hz amplitude-modulated noises with different envelope shapes (ramped: slow attack & sharp decay; damped: sharp attack & slow decay). We observed that subcortical responses did not differ between age groups, whereas older compared to younger adults exhibited larger cortical responses to sound onsets, consistent with an increase in auditory cortical excitability. Neural activity in older adults synchronized more strongly with rapid-onset, slow-offset (damped) envelopes, was less sinusoidal, and more peaked. Younger adults demonstrated the opposite pattern, showing stronger synchronization with slow-onset, rapid-offset (ramped) envelopes, as well as a more sinusoidal neural response shape. The current results suggest that age-related changes in the excitability of auditory cortex alter responses to envelope dynamics. This may be part of the reason why older adults experience difficulty understanding speech in noise.

中文翻译：

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声音对振幅包络的皮质响应随年龄变化

当对语音-声音身份的提示不太多余时，许多年长的听众很难理解噪音中的语音。语音的幅度包络随时间而剧烈波动，并且诸如在开始（攻击）时的幅度变化率和在偏移（衰减）时的幅度变化率就发出了有关语音身份的关键信息。还认为老化会伴随着皮质兴奋性的增加，这可能会不同地改变对包膜动力学的敏感性。在这里，我们记录了（男女两性）年轻人和老年人的脑电图，以研究衰老如何影响神经同步到具有不同包络形状的4 Hz幅度调制噪声（斜率：缓慢发作和急剧衰减；阻尼：剧烈发作和缓慢）衰变）。我们观察到皮层下的反应在各个年龄段之间没有差异，与年长的成年人相比，年龄更大的人对声音发作的皮质反应更大，这与听觉皮质兴奋性的增加相一致。老年人的神经活动与快速发作，缓慢偏移（阻尼）的包膜更紧密地同步，正弦曲线更少，峰值更明显。年轻人表现出相反的模式，表现出与缓慢发作，快速偏移（倾斜）包膜的更强同步性，以及更正弦的神经反应形状。目前的结果表明，与年龄有关的听觉皮层兴奋性变化会改变对包膜动力学的反应。这可能是老年人难以理解噪音语音的部分原因。与听觉皮层兴奋性的增加相一致。老年人的神经活动与快速发作，缓慢偏移（阻尼）的包膜更紧密地同步，正弦曲线更少，峰值更明显。年轻人表现出相反的模式，显示出与缓慢发作，快速偏移（倾斜的）包膜更强的同步性，以及更正弦的神经反应形状。目前的结果表明，与年龄有关的听觉皮层兴奋性变化会改变对包膜动力学的反应。这可能是老年人难以理解噪音语音的部分原因。与听觉皮层兴奋性的增加相一致。老年人的神经活动与快速发作，缓慢偏移（阻尼）的包膜更紧密地同步，正弦曲线更少，峰值更明显。年轻人表现出相反的模式，表现出与缓慢发作，快速偏移（倾斜）包膜的更强同步性，以及更正弦的神经反应形状。目前的结果表明，与年龄有关的听觉皮层兴奋性变化会改变对包膜动力学的反应。这可能是老年人难以理解噪音语音的部分原因。与缓慢发作，快速偏移（倾斜）的包络以及更正弦的神经反应形状显示出更强的同步性。目前的结果表明，与年龄有关的听觉皮层兴奋性变化会改变对包膜动力学的反应。这可能是老年人难以理解噪音语音的部分原因。与缓慢发作，快速偏移（倾斜）的包络以及更正弦的神经反应形状显示出更强的同步性。目前的结果表明，与年龄有关的听觉皮层兴奋性变化会改变对包膜动力学的反应。这可能是老年人难以理解噪音语音的部分原因。