The use of enhanced neural response imaging to get better cochlear implant fitting for children and adults

听力损失较严重的人可以使用人工耳蜗帮助恢复听力-人工耳蜗是一种通过手术植入的设备，可以电刺激耳蜗神经（听觉神经）。该设备的一部分是耳蜗（内耳）内的一组电极。人工耳蜗良好的言语感知取决于听力学家对设备参数的适当调整。对于成年人，最初的拟合通常基于需要患者口头反馈的感知测量。当言语反馈不可能时，参数通常相对于获得可测量的电复合动作电位（ECAP）所需的最低水平进行设置-现代耳蜗植入物可以记录的所有神经纤维的电反应总和。然而，标准的ECAP方法并不能很好地估计感知阈值，因为所使用的刺激速率远低于日常听力所使用的刺激速率;因此，基于ECAP的拟合是次优的。基于我们以前的动物研究，我们提出了一种新的方法来测量ECAP阈值在人类。这种方法涉及测量ECAP的可变性，而不是其平均尺寸，并且更准确和更快。我们将在Selly Oak医院的人工耳蜗植入患者中测试这种方法（伯明翰）和众议院耳朵研究所（洛杉矶）;所有的测试都将与高级仿生学SARL合作，该公司将提供测试患者所需的硬件。我们将联合收割机与计算机模型结合，以预测患者耳蜗不同区域的耳蜗神经纤维数量，并确定来自每个区域的电流如何电极遍布整个耳蜗。需要患者特异性模型来解释例如由潜在病理学、神经存活程度和手术期间电极放置引起的受试者间的显著差异。该模型将用于指导拟合和决定，例如，哪些电极应该是活动的。这种生理和计算技术的结合将克服单独使用ECAP来确定通道相互作用（不同电极产生的神经活动如何重叠）的局限性：使用ECAP来测量通道相互作用的标准使用，纤维分布和电流扩散的影响不能分开。这种区别在临床上是重要的，因为电极不需要仅仅因为低神经存活而变得不活动。在项目期间，这些患者特异性模型将被扩展到预测对更一般刺激的神经活动模式。初始模型将被修改，以便神经纤维由我们先前开发的神经模型模拟。将从模型中选择患者特定的参数来匹配ECAP数据，这将需要开发新的生理方法来提高数据的可靠性。在项目的后期阶段，该模型将用于将感知测量与预测的神经活动相关联，从而更好地理解电和声刺激的感官感知的神经机制。这将导致更好的人工耳蜗设计。由听力学家进行的当代拟合是昂贵的并且不足以使得能够对耳蜗植入参数进行系统的调查。在未来的工作计划中，扩展的患者特异性模型将用于快速突出标准策略的潜在有用参数值，例如最佳刺激速率，并指导新策略的开发。所有上述ECAP方法和模型都将在患者中进行验证，患者可以进行口头反馈。在这个项目中得到的增强拟合程序预计将提高语音清晰度，并导致更好的生活质量的人工耳蜗植入用户。

People with more severe hearing loss can be helped to hear again using a cochlear implant - a surgically implanted device that electrically stimulates the cochlear nerve (the nerve of hearing). Part of the device is a set of electrodes within the cochlea (the inner ear). Good speech perception with cochlear implants depends on appropriate adjustment of device parameters, the fitting , by an audiologist. With adults, the initial fitting is usually based on perceptual measurements that require verbal feedback from the patient. When verbal feedback is not possible, the parameters are typically set relative to the minimum level required to get a measurable electrical compound action potential (ECAP) - the summed electrical response from all the nerve fibres that can be recorded by modern cochlear implants. Standard ECAP methods, however, do not lead to a good estimate of perceptual threshold because the rate of stimulation used is much lower than that used for everyday listening; fitting based on ECAPs is therefore suboptimal. Based on our previous animal studies, we are proposing a new method to measure the ECAP threshold in humans. This method involves measuring the variability of an ECAP rather than its average size and will be both more accurate and faster. We will test the approach with cochlear implants patients from Selly Oak Hospital (Birmingham) and the House Ear Institute (Los Angeles); all tests will be in collaboration with Advanced Bionics SARL who will provide the hardware required to test patients.We will combine this method with a computer model to predict the number of cochlear nerve fibres in different regions of the patient's cochlea and determine how the current from each electrode spreads throughout the cochlea. Patient-specific models are required to account for the substantial intersubject variability arising, for example, from underlying pathology, the degree of nerve survival, and electrode placement during surgery. The model will be used to guide fitting and decide, for example, which electrodes should be active. This combination of physiological and computational techniques will overcome the limitation of using ECAPs alone to determine channel interaction (how the nerve activity generated by different electrodes overlap): With the standard use of ECAPs to gauge channel interaction, the effect of fibre distribution and current spread cannot be separated. Such a distinction is clinically important because electrodes need not be made inactive for low nerve survival alone.During the project, these patient-specific models will be extended to predict the pattern of nerve activity in response to more general stimuli. The initial model will be modified so that nerve fibres are simulated by a nerve model we have previously developed. The patient-specific parameters from the model will be selected to match ECAP data, which will require the development of novel physiological methods to improve the reliability of the data. In the later stages of the project, the model will be used to relate perceptual measures to the predicted nerve activity and therefore enable a greater understanding of neural mechanisms underlying the sensory perception of electrical and acoustic stimulation. This will lead to better cochlear implant design. Contemporary fitting by an audiologist is expensive and insufficient to enable a systematic investigation of cochlear implant parameters. In future programmes of work, extended patient-specific models will be used to quickly highlight potentially useful parameter values for standard strategies, e.g. the optimum stimulation rate, and to guide the development of novel strategies. All the above ECAP methods and models will be validated with patients with whom verbal feedback is possible. The enhanced fitting procedures derived in this project are expected to increase speech intelligibility and lead to a better quality-of-life for cochlear implant users.