Microstructural interactions contribute to the hotspot in the living cochlea

Junpei Liu; Yanru Bai; Qianli Cheng; Shu Zheng; Stephen Elliott; Guangjian Ni

doi:10.1016/j.crneur.2022.100045

Microstructural interactions contribute to the hotspot in the living cochlea

Curr Res Neurobiol. 2022 Jun 20:3:100045. doi: 10.1016/j.crneur.2022.100045. eCollection 2022.

Authors

Junpei Liu^{1

2}, Yanru Bai^{1

2}, Qianli Cheng³, Shu Zheng^{1

2}, Stephen Elliott⁴, Guangjian Ni^{1

3

2}

Affiliations

¹ Academy of Medical Engineering and Translational Medicine, Tianjin University, Tianjin, 300072, China.
² Tianjin Key Laboratory of Brain Science and Neuroengineering, Tianjin, 300072, China.
³ Department of Biomedical Engineering, College of Precision Instruments and Optoelectronics Engineering, Tianjin University, Tianjin, 300072, China.
⁴ Institute of Sound and Vibration Research, University of Southampton, Southampton, SO17 1BJ, UK.

Abstract

The mechanism of the active cochlea relies on a complex interaction between microstructures in the organ of Corti. A significant longitudinal vibration "hotspot" was recently observed in the high-frequency region of the living gerbil cochlea between the Deiters cells and the outer hair cells. A similar phenomenon was also found in guinea pigs with a relatively smaller magnitude. The cause is unknown, but one hypothesis is that this phenomenon is due to the structural constraints between different microstructures. It is not easy to explain the mechanism of hotspots directly from experimental observations. It may also be difficult to image or test if the hotspot will occur in the low-frequency region in the cochlea. We built two three-dimensional finite element models corresponding to the high- and low-frequency regions in the guinea pig cochlea. Responses of the organ of Corti to passive acoustic and outer hair cell electrical excitation were calculated. The two excitations were then superimposed to predict the active response of the organ of Corti. The hotspot phenomenon in the experiment was reproduced and analyzed in-depth about influencing factors. Our results indicate that hotspots appear in the low-frequency region of the cochlea as well. We hypothesize that the hotspot is a locally originated phenomenon in the cochlea, and the traveling wave further enhances the response to low-frequency excitation. The movement of outer hair cells inclined in the longitudinal direction is the leading cause of the hotspot.

Keywords: Finite element model; Hotspot; Low-frequency; Organ of Corti.