Evidence of degraded representation of speech in noise, in the aging midbrain and cortex.
Evidence of degraded representation of speech in noise, in the aging midbrain and cortex.
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DOI：
10.1152/jn.00372.2016
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发表时间：
2016-08
影响因子：
2.5
通讯作者：
A. Presacco;J. Simon;S. Anderson
中科院分区：
文献类型：
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作者：
A. Presacco;J. Simon;S. Anderson
人类在不利条件下（如背景噪音）追踪和理解语音的能力非常出色，但在噪音中理解语音确实会随着年龄的增长而退化。几项研究的结果表明，在年轻人中，低频听觉皮层活动与语音包络可靠地同步，即使背景噪音比语音信号大得多。然而，皮层语言处理可能受到年龄相关的中脑神经同步精度下降的限制。为了更好地理解导致老年人言语感知受损的神经机制，我们研究了在安静和只有一个说话者在场的情况下，衰老如何影响中脑和皮层的言语编码。我们的研究结果表明，中脑和皮层都表现出老年人的中脑颞叶听觉处理缺陷。具体来说，与年轻人相比，老年人在噪音中对语音音节做出反应后的中脑频率下降得更厉害。这表明了中脑听觉机制的失败，而中脑听觉机制需要补偿说话者竞争的存在。同样，在大脑皮层反应中，当有竞争对手加入时，老年人对言语包络的编码能力比年轻人下降得更大。有趣的是，老年人在安静和噪音条件下都表现出夸张的语言皮层表征，这表明抑制和兴奋过程之间可能存在不平衡，或者网络连接减弱可能损害他们有效编码语言的能力。
Humans have a remarkable ability to track and understand speech in unfavorable conditions, such as in background noise, but speech understanding in noise does deteriorate with age. Results from several studies have shown that in younger adults, low-frequency auditory cortical activity reliably synchronizes to the speech envelope, even when the background noise is considerably louder than the speech signal. However, cortical speech processing may be limited by age-related decreases in the precision of neural synchronization in the midbrain. To understand better the neural mechanisms contributing to impaired speech perception in older adults, we investigated how aging affects midbrain and cortical encoding of speech when presented in quiet and in the presence of a single-competing talker. Our results suggest that central auditory temporal processing deficits in older adults manifest in both the midbrain and in the cortex. Specifically, midbrain frequency following responses to a speech syllable are more degraded in noise in older adults than in younger adults. This suggests a failure of the midbrain auditory mechanisms needed to compensate for the presence of a competing talker. Similarly, in cortical responses, older adults show larger reductions than younger adults in their ability to encode the speech envelope when a competing talker is added. Interestingly, older adults showed an exaggerated cortical representation of speech in both quiet and noise conditions, suggesting a possible imbalance between inhibitory and excitatory processes, or diminished network connectivity that may impair their ability to encode speech efficiently.