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Ota T, Nin F, Choi S, Muramatsu S, Sawamura S, Ogata G, Sato MP, Doi K, Doi K, Tsuji T, Kawano S, Reichenbach T, Hibino H. Characterisation of the static offset in the travelling wave in the cochlear basal turn. Pflugers Arch 2020; 472:625-635. [PMID: 32318797 PMCID: PMC7239825 DOI: 10.1007/s00424-020-02373-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Revised: 03/18/2020] [Accepted: 03/23/2020] [Indexed: 02/07/2023]
Abstract
In mammals, audition is triggered by travelling waves that are evoked by acoustic stimuli in the cochlear partition, a structure containing sensory hair cells and a basilar membrane. When the cochlea is stimulated by a pure tone of low frequency, a static offset occurs in the vibration in the apical turn. In the high-frequency region at the cochlear base, multi-tone stimuli induce a quadratic distortion product in the vibrations that suggests the presence of an offset. However, vibrations below 100 Hz, including a static offset, have not been directly measured there. We therefore constructed an interferometer for detecting motion at low frequencies including 0 Hz. We applied the interferometer to record vibrations from the cochlear base of guinea pigs in response to pure tones. When the animals were exposed to sound at an intensity of 70 dB or higher, we recorded a static offset of the sinusoidally vibrating cochlear partition by more than 1 nm towards the scala vestibuli. The offset’s magnitude grew monotonically as the stimuli intensified. When stimulus frequency was varied, the response peaked around the best frequency, the frequency that maximised the vibration amplitude at threshold sound pressure. These characteristics are consistent with those found in the low-frequency region and are therefore likely common across the cochlea. The offset diminished markedly when the somatic motility of mechanosensitive outer hair cells, the force-generating machinery that amplifies the sinusoidal vibrations, was pharmacologically blocked. Therefore, the partition offset appears to be linked to the electromotile contraction of outer hair cells.
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Affiliation(s)
- Takeru Ota
- Department of Molecular Physiology, Niigata University School of Medicine, 1-757 Asahimachi-dori, Chuo-ku, Niigata, 951-8510, Japan
| | - Fumiaki Nin
- Department of Molecular Physiology, Niigata University School of Medicine, 1-757 Asahimachi-dori, Chuo-ku, Niigata, 951-8510, Japan.
| | - Samuel Choi
- AMED-CREST, AMED, Niigata, 951-8510, Japan.,Department of Electrical and Electronics Engineering, Niigata University, Niigata, 950-2181, Japan
| | - Shogo Muramatsu
- Department of Electrical and Electronics Engineering, Niigata University, Niigata, 950-2181, Japan
| | - Seishiro Sawamura
- Department of Molecular Physiology, Niigata University School of Medicine, 1-757 Asahimachi-dori, Chuo-ku, Niigata, 951-8510, Japan
| | - Genki Ogata
- Department of Molecular Physiology, Niigata University School of Medicine, 1-757 Asahimachi-dori, Chuo-ku, Niigata, 951-8510, Japan
| | - Mitsuo P Sato
- Department of Otolaryngology, Kindai University Faculty of Medicine, Osaka, 589-8511, Japan
| | - Katsumi Doi
- Department of Otolaryngology, Kindai University Faculty of Medicine, Osaka, 589-8511, Japan
| | - Kentaro Doi
- Department of Mechanical Science and Bioengineering, Graduate School of Engineering Science, Osaka University, Osaka, 560-8531, Japan
| | - Tetsuro Tsuji
- Department of Mechanical Science and Bioengineering, Graduate School of Engineering Science, Osaka University, Osaka, 560-8531, Japan.,Department of Advanced Mathematical Sciences, Graduate School of Informatics, Kyoto University, Kyoto, 606-8501, Japan
| | - Satoyuki Kawano
- AMED-CREST, AMED, Niigata, 951-8510, Japan.,Department of Mechanical Science and Bioengineering, Graduate School of Engineering Science, Osaka University, Osaka, 560-8531, Japan
| | - Tobias Reichenbach
- Department of Bioengineering, Imperial College London, London, SW7 2AZ, UK
| | - Hiroshi Hibino
- Department of Molecular Physiology, Niigata University School of Medicine, 1-757 Asahimachi-dori, Chuo-ku, Niigata, 951-8510, Japan. .,AMED-CREST, AMED, Niigata, 951-8510, Japan.
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