Mai Guangting, Howell Peter
National Institute for Health Research Nottingham Biomedical Research Centre, Nottingham NG1 5DU, UK; Academic Unit of Mental Health and Clinical Neurosciences, School of Medicine, University of Nottingham, Nottingham NG7 2UH, UK; Department of Experimental Psychology, University College London, London WC1H 0AP, UK.
Department of Experimental Psychology, University College London, London WC1H 0AP, UK.
Hear Res. 2023 Jan;427:108647. doi: 10.1016/j.heares.2022.108647. Epub 2022 Nov 10.
Ageing affects auditory neural phase-locked activities which could increase the challenges experienced during speech-in-noise (SiN) perception by older adults. However, evidence for how ageing affects SiN perception through these phase-locked activities is still lacking. It is also unclear whether influences of ageing on phase-locked activities in response to different acoustic properties have similar or different mechanisms to affect SiN perception. The present study addressed these issues by measuring early-stage phase-locked encoding of speech under quiet and noisy backgrounds (speech-shaped noise (SSN) and multi-talker babbles) in adults across a wide age range (19-75 years old). Participants passively listened to a repeated vowel whilst the frequency-following response (FFR) to fundamental frequency that has primary subcortical sources and cortical phase-locked response to slowly-fluctuating acoustic envelopes were recorded. We studied how these activities are affected by age and age-related hearing loss and how they are related to SiN performances (word recognition in sentences in noise). First, we found that the effects of age and hearing loss differ for the FFR and slow-envelope phase-locking. FFR was significantly decreased with age and high-frequency (≥ 2 kHz) hearing loss but increased with low-frequency (< 2 kHz) hearing loss, whilst the slow-envelope phase-locking was significantly increased with age and hearing loss across frequencies. Second, potential relationships between the types of phase-locked activities and SiN perception performances were also different. We found that the FFR and slow-envelope phase-locking positively corresponded to SiN performance under multi-talker babbles and SSN, respectively. Finally, we investigated how age and hearing loss affected SiN perception through phase-locked activities via mediation analyses. We showed that both types of activities significantly mediated the relation between age/hearing loss and SiN perception but in distinct manners. Specifically, FFR decreased with age and high-frequency hearing loss which in turn contributed to poorer SiN performance but increased with low-frequency hearing loss which in turn contributed to better SiN performance under multi-talker babbles. Slow-envelope phase-locking increased with age and hearing loss which in turn contributed to better SiN performance under both SSN and multi-talker babbles. Taken together, the present study provided evidence for distinct neural mechanisms of early-stage auditory phase-locked encoding of different acoustic properties through which ageing affects SiN perception.
衰老会影响听觉神经的锁相活动，这可能会增加老年人在噪声环境中言语感知（SiN）时所面临的挑战。然而，关于衰老如何通过这些锁相活动影响SiN感知的证据仍然不足。此外，衰老对响应不同声学特性的锁相活动的影响，其影响SiN感知的机制是相似还是不同也尚不清楚。本研究通过测量广泛年龄范围（19 - 75岁）的成年人在安静和嘈杂背景（言语噪声（SSN）和多说话者嘈杂声）下言语的早期锁相编码来解决这些问题。参与者被动聆听重复的元音，同时记录对具有主要皮层下源的基频的频率跟随反应（FFR）以及对缓慢波动的声学包络的皮层锁相反应。我们研究了这些活动如何受到年龄和年龄相关听力损失的影响，以及它们与SiN表现（噪声中句子的单词识别）之间的关系。首先，我们发现年龄和听力损失对FFR和慢包络锁相的影响不同。FFR随着年龄和高频（≥2 kHz）听力损失而显著降低，但随着低频（<2 kHz）听力损失而增加，而慢包络锁相随着年龄和各频率的听力损失而显著增加。其次，锁相活动类型与SiN感知表现之间的潜在关系也不同。我们发现，在多说话者嘈杂声和SSN下，FFR和慢包络锁相分别与SiN表现呈正相关。最后，我们通过中介分析研究了年龄和听力损失如何通过锁相活动影响SiN感知。我们表明，这两种活动都显著介导了年龄/听力损失与SiN感知之间的关系，但方式不同。具体而言，FFR随着年龄和高频听力损失而降低，这反过来导致SiN表现较差，但随着低频听力损失而增加，这反过来在多说话者嘈杂声下导致SiN表现较好。慢包络锁相随着年龄和听力损失而增加，这反过来在SSN和多说话者嘈杂声下都导致SiN表现较好。综上所述，本研究为衰老影响SiN感知的不同声学特性的早期听觉锁相编码的不同神经机制提供了证据。
