1
|
Castle N, Liang J, Smith M, Petersen B, Matson C, Eldridge T, Zhang K, Lee CH, Liu Y, Dai C. Finite Element Modeling of Residual Hearing after Cochlear Implant Surgery in Chinchillas. Bioengineering (Basel) 2023; 10:bioengineering10050539. [PMID: 37237608 DOI: 10.3390/bioengineering10050539] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Revised: 04/20/2023] [Accepted: 04/24/2023] [Indexed: 05/28/2023] Open
Abstract
Cochlear implant (CI) surgery is one of the most utilized treatments for severe hearing loss. However, the effects of a successful scala tympani insertion on the mechanics of hearing are not yet fully understood. This paper presents a finite element (FE) model of the chinchilla inner ear for studying the interrelationship between the mechanical function and the insertion angle of a CI electrode. This FE model includes a three-chambered cochlea and full vestibular system, accomplished using µ-MRI and µ-CT scanning technologies. This model's first application found minimal loss of residual hearing due to insertion angle after CI surgery, and this indicates that it is a reliable and helpful tool for future applications in CI design, surgical planning, and stimuli setup.
Collapse
Affiliation(s)
- Nicholas Castle
- Department of Aerospace and Mechanical Engineering, University of Oklahoma, Norman, OK 73019, USA
| | - Junfeng Liang
- Department of Aerospace and Mechanical Engineering, University of Oklahoma, Norman, OK 73019, USA
| | - Matthew Smith
- Department of Aerospace and Mechanical Engineering, University of Oklahoma, Norman, OK 73019, USA
| | - Brett Petersen
- Department of Aerospace and Mechanical Engineering, University of Oklahoma, Norman, OK 73019, USA
| | - Cayman Matson
- Department of Aerospace and Mechanical Engineering, University of Oklahoma, Norman, OK 73019, USA
| | - Tara Eldridge
- Department of Aerospace and Mechanical Engineering, University of Oklahoma, Norman, OK 73019, USA
| | - Ke Zhang
- Department of Aerospace and Mechanical Engineering, University of Oklahoma, Norman, OK 73019, USA
| | - Chung-Hao Lee
- Department of Aerospace and Mechanical Engineering, University of Oklahoma, Norman, OK 73019, USA
| | - Yingtao Liu
- Department of Aerospace and Mechanical Engineering, University of Oklahoma, Norman, OK 73019, USA
| | - Chenkai Dai
- Department of Aerospace and Mechanical Engineering, University of Oklahoma, Norman, OK 73019, USA
| |
Collapse
|
2
|
Zhou W, Jabeen T, Sabha S, Becker J, Nam JH. Deiters Cells Act as Mechanical Equalizers for Outer Hair Cells. J Neurosci 2022; 42:8361-8372. [PMID: 36123119 PMCID: PMC9653280 DOI: 10.1523/jneurosci.2417-21.2022] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 09/06/2022] [Accepted: 09/11/2022] [Indexed: 11/21/2022] Open
Abstract
The outer hair cells in the mammalian cochlea are cellular actuators essential for sensitive hearing. The geometry and stiffness of the structural scaffold surrounding the outer hair cells will determine how the active cells shape mammalian hearing by modulating the organ of Corti (OoC) vibrations. Specifically, the tectorial membrane and the Deiters cell are mechanically in series with the hair bundle and soma, respectively, of the outer hair cell. Their mechanical properties and anatomic arrangement must determine the relative motion among different OoC structures. We measured the OoC mechanics in the cochleas acutely excised from young gerbils of both sexes at a resolution fine enough to distinguish the displacement of individual cells. A three-dimensional finite element model of fully deformable OoC was exploited to analyze the measured data in detail. As a means to verify the computer model, the basilar membrane deformations because of static and dynamic stimulations were measured and simulated. Two stiffness ratios have been identified that are critical to understand cochlear physics, which are the stiffness of the tectorial membrane with respect to the hair bundle and the stiffness of the Deiters cell with respect to the outer hair cell body. Our measurements suggest that the Deiters cells act like a mechanical equalizer so that the outer hair cells are constrained neither too rigidly nor too weakly.SIGNIFICANCE STATEMENT Mammals can detect faint sounds thanks to the action of mammalian-specific receptor cells called the outer hair cells. It is getting clearer that understanding the interactions between the outer hair cells and their surrounding structures such as the tectorial membrane and the Deiters cell is critical to resolve standing debates. Depending on theories, the stiffness of those two structures ranges from negligible to rigid. Because of their perceived importance, their properties have been measured in previous studies. However, nearly all existing data were obtained ex situ (after they were detached from the outer hair cells), which obscures their interaction with the outer hair cells. We quantified the mechanical properties of the tectorial membrane and the Deiters cell in situ.
Collapse
Affiliation(s)
| | - Talat Jabeen
- Biomedical Engineering, University of Rochester, Rochester, New York 14627
| | | | | | - Jong-Hoon Nam
- Departments of Mechanical Engineering
- Biomedical Engineering, University of Rochester, Rochester, New York 14627
- Neuroscience Program, University of Rochester Medical Center, Rochester, New York 14627
| |
Collapse
|
3
|
Sisto R, Belardinelli D, Moleti A. Fluid focusing and viscosity allow high gain and stability of the cochlear response. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2021; 150:4283. [PMID: 34972263 DOI: 10.1121/10.0008940] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Accepted: 11/11/2021] [Indexed: 06/14/2023]
Abstract
This paper discusses the role of two-dimensional (2-D)/three-dimensional (3-D) cochlear fluid hydrodynamics in the generation of the large nonlinear dynamical range of the basilar membrane (BM) and pressure response, in the decoupling between cochlear gain and tuning, and in the dynamic stabilization of the high-gain BM response in the peak region. The large and closely correlated dependence on stimulus level of the BM velocity and fluid pressure gain [Dong, W., and Olson, E. S. (2013). Biophys. J. 105(4), 1067-1078] is consistent with a physiologically oriented schematization of the outer hair cell (OHC) mechanism if two hydrodynamic effects are accounted for: amplification of the differential pressure associated with a focusing phenomenon, and viscous damping at the BM-fluid interface. The predictions of the analytical 2-D Wentzel-Kramers-Brillouin (WKB) approach are compared to solutions of a 3-D finite element model, showing that these hydrodynamic phenomena yield stable high-gain response in the peak region and a smooth transition among models with different effectiveness of the active mechanism, mimicking the cochlear nonlinear response over a wide stimulus level range. This study explains how an effectively anti-damping nonlinear outer hair cells (OHC) force may yield large BM and pressure dynamical ranges along with an almost level-independent admittance.
Collapse
Affiliation(s)
- Renata Sisto
- INAIL, Department of Medicine, Epidemiology and Hygiene, Monte Porzio Catone (RM), Italy
| | - Daniele Belardinelli
- INAIL, Department of Medicine, Epidemiology and Hygiene, Monte Porzio Catone (RM), Italy
| | - Arturo Moleti
- Physics Department, University of Rome Tor Vergata, Rome, Italy
| |
Collapse
|
4
|
Murakami Y. Fast time-domain solution of a nonlinear three-dimensional cochlear model using the fast Fourier transform. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2021; 150:2589. [PMID: 34717501 DOI: 10.1121/10.0006533] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2021] [Accepted: 09/13/2021] [Indexed: 06/13/2023]
Abstract
A fast numerical time-domain solution of a nonlinear three-dimensional (3D) cochlear model is proposed. In dynamical systems, a time-domain solution can determine nonlinear responses, and the human faculty of hearing depends on nonlinear behaviors of the microscopically structured organs of the cochlea. Thus, time-domain 3D modeling can help explain hearing. The matrix product, an n2 operation, is a central part of the time-domain solution procedure in cochlear models. To solve the cochlear model faster, the fast Fourier transform (FFT), an n log n operation, is used to replace the matrix product. Numerical simulation results verified the similarity of the matrix product and the FFT under coarse grid settings. Furthermore, applying the FFT reduced the computation time by a factor of up to 100 owing to the computational complexity of the proposed approach being reduced from n2 to n log n. Additionally, the proposed method successfully computed 3D models under moderate and fine grid settings that were unsolvable using the matrix product. The 3D cochlear model exhibited nonlinear responses for pure tones and clicks under various gain distributions in a time-domain simulation. Thus, the FFT-based method provides fast numerical solutions and supports the development of 3D models for cochlear mechanics.
Collapse
Affiliation(s)
- Yasuki Murakami
- Faculty of Design, Kyushu University, 4-9-1 Shiobaru, Minamiku, Fukuoka 815-8540, Japan
| |
Collapse
|
5
|
Shokrian M, Knox C, Kelley DH, Nam JH. Mechanically facilitated micro-fluid mixing in the organ of Corti. Sci Rep 2020; 10:14847. [PMID: 32908205 PMCID: PMC7481204 DOI: 10.1038/s41598-020-71380-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Accepted: 08/06/2020] [Indexed: 12/27/2022] Open
Abstract
The cochlea is filled with two lymphatic fluids. Homeostasis of the cochlear fluids is essential for healthy hearing. The sensory epithelium called the organ of Corti separates the two fluids. Corti fluid space, extracellular fluid space within the organ of Corti, looks like a slender micro-tube. Substantial potassium ions are constantly released into the Corti fluid by sensory receptor cells. Excess potassium ions in the Corti fluid are resorbed by supporting cells to maintain fluid homeostasis. Through computational simulations, we investigated fluid mixing within the Corti fluid space. Two assumptions were made: first, there exists a longitudinal gradient of potassium ion concentration; second, outer hair cell motility causes organ of Corti deformations that alter the cross-sectional area of the Corti fluid space. We hypothesized that mechanical agitations can accelerate longitudinal mixing of Corti fluid. Corti fluid motion was determined by solving the Navier–Stokes equations incorporating nonlinear advection term. Advection–diffusion equation determined the mixing dynamics. Simulating traveling boundary waves, we found that advection and diffusion caused comparable mixing when the wave amplitude and speed were 25 nm and 7 m/s, respectively. Higher-amplitude and faster waves caused stronger advection. When physiological traveling waves corresponding to 70 dB sound pressure level at 9 kHz were simulated, advection speed was as large as 1 mm/s in the region basal to the peak responding location. Such physiological agitation accelerated longitudinal mixing by more than an order of magnitude, compared to pure diffusion. Our results suggest that fluid motion due to outer hair cell motility can help maintain longitudinal homeostasis of the Corti fluid.
Collapse
Affiliation(s)
- Mohammad Shokrian
- Department of Mechanical Engineering, University of Rochester, 203 Hopeman Engineering Bldg, Rochester, NY, 14627, USA
| | - Catherine Knox
- Department of Mechanical Engineering, University of Rochester, 203 Hopeman Engineering Bldg, Rochester, NY, 14627, USA
| | - Douglas H Kelley
- Department of Mechanical Engineering, University of Rochester, 203 Hopeman Engineering Bldg, Rochester, NY, 14627, USA
| | - Jong-Hoon Nam
- Department of Mechanical Engineering, University of Rochester, 203 Hopeman Engineering Bldg, Rochester, NY, 14627, USA. .,Department of Biomedical Engineering, University of Rochester, Rochester, NY, USA. .,Department of Neuroscience, University of Rochester, Rochester, NY, USA.
| |
Collapse
|
6
|
Ni G, Pang J, Zheng Q, Xu Z, Liu B, Zhang H, Ming D. Modeling cochlear micromechanics: hypotheses and models. JOURNAL OF BIO-X RESEARCH 2019. [DOI: 10.1097/jbr.0000000000000034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
|