Characterization and Modelling of the Electrode-Nerve Interface for Electro-Acoustic Stimulation in Cochlear Implant Users

如今，越来越多的剩余听力患者接受人工耳蜗术，以获得电声刺激(EAS)，即通过CI电极提供的电刺激和通过助听器(HA)提供的声刺激相结合的听觉刺激。对于EAS用户来说，低频声学听力几乎不能识别噪声中的语音，但与CI提供的电子听力相结合时，性能会显著提高。然而，声刺激和电刺激是如何相互作用的，目前还不清楚。临床经验发现，部分EAS使用者根本不使用HA，仅依靠电刺激。此外，已经观察到，EAS用户需要比普通CI用户更多的时间来单独使用CI来实现其最大性能。这些限制可能对确定EAS的植入标准产生影响。这些局限性的可能解释是声刺激和电刺激之间的相互作用。这些相互作用对于残留听力较大的人来说变得越来越重要，因为电刺激和声刺激之间的重叠更大。例如，已有研究表明，指定EAS设备治疗的听力损失范围正越来越接近与年龄相关的听力损失范围。老年性听力损失，如EAS，以高频段听力丧失为特征。鉴于欧洲人口老龄化，与听力损失相关的问题日益增多，需要新的治疗方法来恢复与年龄相关的听力损失。认知衰退和听力损失似乎是相关的，新的治疗方法，如EAS，非常有希望改善老年人的生活质量。这项工作是关于描述声刺激和电刺激之间的相互作用。特征将包括EAS用户的心理物理、电生理、成像和反向遥测措施。在心理物理上，声和电的相互作用将通过同步或前向掩蔽实验来测量。每个研究参与者的锥形束计算机断层扫描(CBCT)将被用来评估插入深度和电极位置。将使用植入物反向遥测的电场成像(EFI)来表征电极神经元界面，最后将使用电子耳蜗术(EChochG)测量来评估神经水平上的声和电刺激之间的重叠。该项目的结果是数据集、拟合程序和描述每个EAS用户的声和电刺激之间相互作用的模型。这些结果应用于优化EAS设备的配置，并评估EAS植入的适应症是否有可能扩展到年龄相关性听力损失的人。

Everyday more people with residual hearing receive cochlear implants (CIs) to obtain electroacoustic stimulation (EAS), i.e. combined auditory stimulation delivered electrically from CI electrodes and acoustically through a hearing aid (HA). For EAS users low frequency acoustic hearing produces almost no recognition for speech in noise, but the performance is significantly enhanced when combined with the electric hearing delivered by the CI. However, it is still unknown how the acoustic and electric stimulation modalities interact with each other. Clinical experience has found that some EAS users do not use the HA at all and rely solely on electric stimulation. Moreover, it has been observed that EAS users require more time to achieve their maximum performance with the CI alone than regular CI users. These limitations may have influence in defining the implantation criteria of EAS. Possible explanations for these limitations are interactions between acoustic and electric stimulation. These interactions become more and more important for people with large residual hearing because the overlap between electric and acoustic stimulation is larger. For example, it has been shown that the range of hearing loss for which EAS devices are prescribed is getting closer to the range of age related hearing loss. Age related hearing loss, as EAS, is characterized by lost of audibility in the high frequencies. Given that the population in Europe is becoming older with increased hearing loss related problems new treatments are required to rehabilitate people with age related hearing loss. Cognitive decline and hearing loss seem to be related and new treatments such as EAS are very promising to improve quality of life of the elderly population. This work is about characterizing the interaction between acoustic and electric stimulation. The characterization will consist of psychophysical, electrophysiological, imaging and backward telemetry measures in EAS users. Psychophysically, the acoustic and electric interaction will be measured by means of simultaneous or forward masking experiments. Cone beam computer tomography (CBCT) for each study participant will be used to assess the insertion depth and electrode positions. Electrical field imaging (EFI) from the backward telemetry of the implant will be used to characterize the electrode neuron interface, and finally electrocochleography (eChochG) measures will be used to assess the overlap between acoustic and electric stimulation at the neural level. The outcomes of this project are datasets, fitting procedures and a model characterizing the interaction between acoustic and electric stimulation of each EAS user. These outcomes have application to optimize the configuration of EAS devices and to assess whether the indication for EAS implantation can be potentially extended to people with age related hearing loss.