Glia as regulators of auditory nerve function

哺乳动物具有非凡的分析环境声音的能力，这为它们的生存提供了重要的优势。人类的听觉似乎最适合用于语音交流的声音频率范围，这也与我们对音乐的欣赏有关。听觉的感觉器官，“耳蜗”，分析传入的声波，并通过听觉神经内的兴奋细胞群向大脑发送电子编码信号。我们需要的所有必要信息来理解音高、响度、声音的来源等，都包含在神经传递给大脑的电子代码的细节中。神经细胞能够以非常高的速率持续工作，并且多年不被替换，因为它们所处的环境是由被称为“神经胶质”的非感觉细胞保持稳定的。来自神经系统其他地方的证据表明，在神经细胞和伴随它们的神经胶质细胞之间存在着持续的交流，这可以通知神经胶质细胞对神经活动的变化做出反应。耳蜗中发生这种情况的细节尚不清楚。这种神经胶质细胞间交流的失败被认为会导致神经细胞死亡和慢性疼痛等疾病。神经胶质还负责给神经细胞涂上一层叫做髓磷脂的绝缘层。髓磷脂的作用就像家用电线上的塑料涂层一样，可以提高电导率，并在信号长距离传输时将能量损失降到最低。人们认为髓磷脂在发育过程中形成的方式是神经功能成熟的重要线索。这对我们理解人类感觉功能的开始具有重要意义，特别是与听力的发展有关。该项目旨在更好地了解耳蜗中的神经胶质功能，以及神经胶质如何保存听神经中的基本信号。这项研究的数据将有助于解释正常听力的一些复杂性，并可能确定旨在提高内耳神经细胞存活率的治疗的潜在目标。此外，该项目将有助于未来设计诸如人工耳蜗之类的设备。对于一些失去听力的人来说，神经胶质保证了耳聋中一些神经细胞的存活，甚至在耳聋首次出现后的数年里。这种存活意味着神经可以通过人工耳蜗进行电刺激，为重度聋人提供一些听力。胶质细胞显然在听力和耳聋中都很重要，但目前还不清楚它们是如何发挥这些重要作用的。不过，这项研究的结果并不仅限于听力，因为许多待研究的机制在整个神经系统中都很常见。对神经胶质细胞功能的更全面了解，将对其他研究神经系统（包括其他感觉器官和大脑）的科学家和临床医生有价值。

Mammals have an extraordinary ability to analyse the sounds within their environment and this can provide them with important advantages for survival. Humans hearing appears best-tuned to the range of sound frequencies that are used for speech-based communication, and this is also relevant for our appreciation of music. The sensory organ of hearing, the "cochlea", analyses incoming sound waves and sends electrically coded signals to the brain via groups of excitable cells within the auditory nerve. All the necessary information we require to understand the pitch, loudness, site of origin of sounds etc, are carried within the fine detail of the electrical code that the nerve passes to the brain. The nerve cells are able to work continually, at very high rates, and for many years without being replaced, because the environment they inhabit is kept stable by non-sensory cells called "glia". There is evidence from elsewhere in the nervous system that there is continual communication between nerve cells and their attendant glia, and that this can inform glia to be reactive to changes in nerve activity. The details of how this happens in the cochlea are unknown. Failures of this nerve-glia communication are suggested to cause death of nerve cells and conditions such as chronic pain. Glia are also responsible for coating the nerve cells with an insulating layer called "myelin". Myelin acts like the plastic coating on household wires, to improve electrical conductivity and to minimise energy losses as signals are carried over long distances. It is thought that the way in which myelin is laid down during development acts as an important cue for the maturation of nerve function. This has important implications for our understanding of the onset of sensory function in humans, and is particularly relevant to how hearing develops. This project is aimed towards a better understanding of glial function in the cochlea, and how glia preserve essential signalling in the auditory nerve. The data from this study would help explain some of the complexities of normal hearing, and may identify potential targets for therapies aimed at enhancing nerve cell survival in the inner ear. In addition the project would assist in the future design of devices such as cochlear implants. In some people who have lost their hearing the glia ensure the survival of some of the nerve cells in the deafened ear, even for years after deafness first occurs. This survival means the nerves can be electrically stimulated via a cochlear implant, providing the profoundly deaf with some hearing. Glia are clearly important in both the hearing and deaf ear, but it is not currently obvious how they carry out these essential roles. The findings of the study would not be specific to hearing though, as many of the mechanisms to be studied are common throughout the nervous system. A more comprehensive picture of how glial cells function would be of value to other scientists and clinicians studying the nervous system, including the other sense organs and the brain.