Development of the program for analysis of the dynamic behavior of the organ of Corti

2002 Fiscal Year Final Research Report Summary

• Project/Area Number: 13557142
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 展開研究
• Research Field: Otorhinolaryngology
• Research Institution: Tohoku University
• Principal Investigator: WADA Hiroshi Tohoku University Graduate School of Engineering, Professor, 大学院・工学研究科, 教授 (30111264)
• Co-Investigator(Kenkyū-buntansha): KOIKE Takuji The University of Electro-Communications, Department of Mechanical Engineering and Intelligent Systems, Associate Professor, 知能機械工学科, 助教授 (10282097) ; KAWASE Tetsuaki Tohoku University Graduate School of Medicine, Associate Professor, 大学院・医学系研究科, 助教授 (50169728)
• Project Period (FY): 2001 – 2002
• Keywords: cochlea / organ of Corti / dynamic behavior / FEM / fluid-structure interaction

Research Abstract

The organ of Corti (OC) in the cochlea transforms sounds into action potentials in auditory nerve fibers. As the extreme vulnerability to trauma exhibited by the cochlea prevents the experimental observation that could confirm the inherence in this process, the two-dimensional finite-element model of the OC was constructed. Using this model, the dynamic behavior of the OC was analyzed.
As the DC is immersed in lymph fluid, the interaction between the OC and the lymph fluid must be taken into account when the dynamic behavior of the OC and fluid pressure distribution are numerically analyzed. However, the complex structure of the OC and the large difference in material properties between the fluid and the structure of the OC complicate modeling of the lymph-OC interaction using commercially available FEN applications. Therefore, the original program was developed to consider the fluid-structure interaction.
When a fluid pressure fluctuation is induced by vibration of the stapes, two types of pressure waves occur in the cochlea. As the OC is driven by these pressure waves, it is important to understand their frequency characteristics. However, there have been no reports on empirical observations of these waves, because of the difficulty of measuring them independently. Using the model, the magnitude and phase of the fast and slow waves were predicted so as to fit the numerically obtained pressure distribution in the scala tympani with that of the intracochlea pressure measurement. Next, the dynamic behavior of the OC was analyzed when these predicted pressures were applied to the OC. The following conclusions can be drawn:
1. The magnitude of the fast wave increases with increasing frequency for the entire frequency range. The magnitude of the slow wave increases gradually with increasing frequency until it reaches a maximum at the characteristic frequency (CF), and it then falls sharply.
2. The OC shows a rotational movement around the end of the modiolus side of the basilar membrane.