Sensory consequences of ageing on the neurobiology of speech perception

到70岁时，71%的人会经历不同程度的听力损失，这可能会导致生活质量的严重变化。我们都经历过在背景噪音中难以理解语音的挫折感。对于听力受损的老年人来说尤其如此，他们更有可能脱离在嘈杂环境中进行的社交活动，增加社交孤立，降低精神健康。事实上，几项研究已经发现听力损失和大脑健康下降之间存在显著关系。我们需要关于年龄相关性听力损失如何影响大脑的新知识，以便开发有效的干预措施。听力损失通常反映出耳朵中毛细胞的问题，这降低了语音信号被耳朵分解的方式。这意味着退化的信号随后被发送到大脑。然后，我们的大脑必须努力工作，才能收听演讲并理解其中的信息。这有点像使用调谐拨盘调谐到广播电台。然而，我们不知道听力损失是如何影响我们大脑的调谐能力的。我们需要知道这一点，以便开发有效的干预措施来治疗与年龄相关的听力损失。我的第一个研究问题是找出大脑较高级别的听觉区域是否有助于调整语言在听觉系统较低级别区域的表达方式。了解第一个调谐机制是否被破坏或起作用将有助于澄清哪种类型的基于计算机的听觉训练程序将最有效地帮助听力损失的人。我的第二个研究问题是找出大脑较高级别的运动区是否有助于调整语言在较高级别的听觉区域的表现方式。了解第二个调谐机制是否被破坏或起作用，将有助于澄清干预策略是针对支持剩余的听觉资源，还是另外针对支持代偿性运动资源，如发音训练，以加强言语运动通路和听觉信息之间的联系。我的第三个研究问题是，我们是否可以改进与注意力挂钩的调谐机制，帮助我们保持专注于言语，忽略嘈杂地方的背景声音。知道我们能否改进这第三种调谐机制是很重要的，因为如果我们能改进它，它可能代表着一种新的干预年龄相关性听力损失的途径。我将使用大脑刺激来操纵大脑是如何工作的。例如，我将使用大脑刺激来增加或减少大脑高级听力区域的活动。大脑刺激的工作原理是对大脑施加磁脉冲，这可以暂时且安全地影响大脑特定区域的脑细胞如何协同工作。我将使用大脑成像来拍摄大脑中的电活动如何受到大脑刺激的影响。最后，我将使用行为任务来记录人们在大脑刺激后听到和识别语言的能力。通过比较刺激前后的大脑成像和行为，我将能够判断刺激大脑较高级别区域是否会影响年龄相关性听力损失患者的调谐(使用大脑成像)和行为(使用听力和听力测试)。

By the age of 70 years, 71% of people experience some degree of hearing loss, which can cause severe changes to quality of life. We have all experienced the frustration of struggling to understand speech in background noise. This is particularly true for older adults with hearing loss, who are more likely to disengage from social interactions that take place in noisy environments, increasing social isolation and decreasing mental wellbeing. Indeed, several studies have found a significant relation between hearing loss and reduced brain health. We need new knowledge of how age-related hearing loss affects the brain in order to develop effective interventions.Hearing loss usually reflects a problem with hair cells in the ear, which degrades how the speech signal is broken down by the ear. This means that a degraded signal is subsequently sent to the brain. Our brains then have to work hard to tune in on the speech and understand the message. This is a bit like using a tuning dial to tune into a radio station. However, we do not know how our brain's tuning ability is affected by hearing loss. We need to know this in order to develop effective interventions for age-related hearing loss.My first research question is to find out if the higher-level auditory areas of the brain help to tune the way speech is represented in lower-level areas of the auditory system. Knowing whether this first tuning mechanism is broken or functioning will help to clarify what type of computer-based auditory training program will work best to help people with hearing loss.My second research question is to find out if higher-level motor areas of the brain help to tune the way speech is represented in higher-level auditory areas. Knowing whether this second tuning mechanism is broken or functioning will help to clarify whether intervention strategies should be geared towards supporting remaining auditory resources, or additionally towards supporting compensatory motor resources, such as articulation training to strengthen the link between speech motor pathways and auditory information.My third research question is to find out whether we can improve a tuning mechanism linked to attention that helps us to keep focused on speech and ignore background sounds in noisy places. Knowing whether we can improve this third tuning mechanism is important because if we can improve it, it could represent a new intervention pathway for age-related hearing loss.To answer these questions, I will combine three major lines of enquiry. I will use brain stimulation to manipulate how the brain is working. For example, I will use brain stimulation to increase or decrease activity in the higher-level hearing areas of the brain. Brain stimulation works by applying magnetic pulses to the brain, which can temporarily, and safely, affect how the brain cells work together in a particular area of the brain. I will use brain imaging to take a picture of how electrical activity in the brain has been affected by the brain stimulation. I will lastly use behavioural tasks to record people's ability to hear and recognise speech after the brain stimulation. By comparing brain imaging and behaviour before and after the stimulation, I will be able to tell if stimulation of higher-level areas of the brain affects tuning (using brain imaging), and behaviour (using hearing and listening tests) in people with age-related hearing loss.