Sensory consequences of ageing on the neurobiology of speech perception

点击翻译按钮获取中文摘要

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.