Graduate School of Engineering Science, Osaka University, Osaka, Japan.
Int J Numer Method Biomed Eng. 2021 Dec;37(12):e3430. doi: 10.1002/cnm.3430. Epub 2021 Jan 7.
We report a novel mathematical model of an artificial auditory system consisting of a micro-machined cochlea and the auditory nerve response it evokes. The modeled micro-machined cochlea is one previously realized experimentally by mimicking functions of the cochlea [Shintaku et al, Sens. Actuat. 158 (2010) 183-192; Inaoka et al, Proc. Natl. Acad. Sci. USA 108 (2011) 18390-18395]. First, from the viewpoint of mechanical engineering, the frequency characteristics of a model device were experimentally investigated to develop an artificial basilar membrane based on a spring-mass-damper system. In addition, a nonlinear feedback controller mimicking the function of the outer hair cells was incorporated in this experimental system. That is, the developed device reproduces the proportional relationship between the oscillation amplitude of the basilar membrane and the cube root of the sound pressure observed in the mammalian auditory system, which is what enables it to have a wide dynamic range, and the characteristics of the control performance were evaluated numerically and experimentally. Furthermore, the stimulation of the auditory nerve by the micro-machined cochlea was investigated using the present mathematical model, and the simulation results were compared with our previous experimental results from animal testing [Shintaku et al, J. Biomech. Sci. Eng. 8 (2013) 198-208]. The simulation results were found to be in reasonably good agreement with those from the previous animal test; namely, there exists a threshold at which the excitation of the nerve starts and a saturation value for the firing rate under a large input. The proposed numerical model was able to qualitatively reproduce the results of the animal test with the micro-machined cochlea and is thus expected to guide the evaluation of micro-machined cochleae for future animal experiments.
我们报告了一个由微机械耳蜗和听觉神经反应组成的人工听觉系统的新数学模型。所建模的微机械耳蜗是之前通过模拟耳蜗功能而实验实现的[Shintaku 等人，Sens. Actuat. 158（2010）183-192；Inaoka 等人，Proc. Natl. Acad. Sci. USA 108（2011）18390-18395]。首先，从机械工程的角度出发，通过实验研究了模型装置的频率特性，以开发基于弹簧-质量-阻尼系统的人工基底膜。此外，在这个实验系统中还包含了一个模仿外毛细胞功能的非线性反馈控制器。也就是说，所开发的装置再现了哺乳动物听觉系统中观察到的基底膜振动幅度与声压立方根之间的比例关系，这使其具有较宽的动态范围，并且评估了控制性能的数值和实验特性。此外，使用本数学模型研究了微机械耳蜗对听觉神经的刺激，并且将模拟结果与我们之前的动物实验结果进行了比较[Shintaku 等人，J. Biomech. Sci. Eng. 8（2013）198-208]。模拟结果与之前的动物测试结果非常吻合；也就是说，存在一个激发神经的起始阈值和一个大输入下的发放率饱和值。所提出的数值模型能够定性地再现带有微机械耳蜗的动物测试结果，因此有望为未来的动物实验指导微机械耳蜗的评估。
