1
|
O’Connell-Rodwell CE, Berezin JL, Dharmarajan A, Ravicz ME, Hu Y, Guan X, O’Connor KN, Puria S. The impact of size on middle-ear sound transmission in elephants, the largest terrestrial mammal. PLoS One 2024; 19:e0298535. [PMID: 38598472 PMCID: PMC11006165 DOI: 10.1371/journal.pone.0298535] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Accepted: 01/25/2024] [Indexed: 04/12/2024] Open
Abstract
Elephants have a unique auditory system that is larger than any other terrestrial mammal. To quantify the impact of larger middle ear (ME) structures, we measured 3D ossicular motion and ME sound transmission in cadaveric temporal bones from both African and Asian elephants in response to air-conducted (AC) tonal pressure stimuli presented in the ear canal (PEC). Results were compared to similar measurements in humans. Velocities of the umbo (VU) and stapes (VST) were measured using a 3D laser Doppler vibrometer in the 7-13,000 Hz frequency range, stapes velocity serving as a measure of energy entering the cochlea-a proxy for hearing sensitivity. Below the elephant ME resonance frequency of about 300 Hz, the magnitude of VU/PEC was an order of magnitude greater than in human, and the magnitude of VST/PEC was 5x greater. Phase of VST/PEC above ME resonance indicated that the group delay in elephant was approximately double that of human, which may be related to the unexpectedly high magnitudes at high frequencies. A boost in sound transmission across the incus long process and stapes near 9 kHz was also observed. We discuss factors that contribute to differences in sound transmission between these two large mammals.
Collapse
Affiliation(s)
- Caitlin E. O’Connell-Rodwell
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Harvard Medical School, Boston, Massachusetts, United States of America
- Department of Otolaryngology, Head & Neck Surgery, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Jodie L. Berezin
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Anbuselvan Dharmarajan
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Michael E. Ravicz
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Harvard Medical School, Boston, Massachusetts, United States of America
- Department of Otolaryngology, Head & Neck Surgery, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Yihan Hu
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Xiying Guan
- School of Medicine, Wayne State University, Detroit, Michigan, United States of America
| | - Kevin N. O’Connor
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Sunil Puria
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Harvard Medical School, Boston, Massachusetts, United States of America
- Department of Otolaryngology, Head & Neck Surgery, Harvard Medical School, Boston, Massachusetts, United States of America
- Graduate Program in Speech and Hearing and Biosciences and Technologies, Harvard Medical School, Boston, Massachusetts, United States of America
| |
Collapse
|
2
|
O'Connell-Rodwell CE, Berezin JL, Dharmarajan A, Ravicz ME, Hu Y, Guan X, O'Connor KN, Puria S. The impact of size on middle-ear sound transmission in elephants, the largest terrestrial mammal. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.25.559337. [PMID: 37808830 PMCID: PMC10557572 DOI: 10.1101/2023.09.25.559337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/10/2023]
Abstract
Elephants have a unique auditory system that is larger than any other terrestrial mammal. To quantify the impact of larger middle ear (ME) structures, we measured 3D ossicular motion and ME sound transmission in cadaveric temporal bones from both African and Asian elephants in response to air-conducted (AC) tonal pressure stimuli presented in the ear canal (P EC ). Results were compared to similar measurements in humans. Velocities of the umbo (V U ) and stapes (V ST ) were measured using a 3D laser Doppler vibrometer in the 7-13,000 Hz frequency range, stapes velocity serving as a measure of energy entering the cochlea-a proxy for hearing sensitivity. Below the elephant ME resonance frequency of about 300 Hz, the magnitude of V U /P EC was an order of magnitude greater than in human, and the magnitude of V ST /P EC was 5x greater. Phase of V ST /P EC above ME resonance indicated that the group delay in elephant was approximately double that of human, which may be related to the unexpectedly high magnitudes at high frequencies. A boost in sound transmission across the incus long process and stapes near 9 kHz was also observed. We discuss factors that contribute to differences in sound transmission between these two large mammals.
Collapse
|
3
|
Rosowski JJ, Ramier A, Cheng JT, Yun SH. Optical coherence tomographic measurements of the sound-induced motion of the ossicular chain in chinchillas: Additional modes of ossicular motion enhance the mechanical response of the chinchilla middle ear at higher frequencies. Hear Res 2020; 396:108056. [PMID: 32836020 PMCID: PMC7572631 DOI: 10.1016/j.heares.2020.108056] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 07/18/2020] [Accepted: 08/06/2020] [Indexed: 10/23/2022]
Abstract
Wavelength-swept optical coherence tomography (OCT) was used to scan the structure of cadaveric chinchilla ears in three dimensions with high spatial resolution and measure the sound-induced displacements of the entire OCT-visible lateral surfaces of the ossicles in the lateral-to-medial direction. The simultaneous measurement of structure and displacement allowed a precise match between the observed motion and its structural origin. The structure and measured displacements are consistent with previously published data. The coincident detailed structural and motion measurements demonstrate the presence of several frequency-dependent modes of ossicular motion, including: (i) rotation about an anteriorly-to-posteriorly directed axis positioned near the commonly defined anatomical axis of rotation that dominates at frequencies below 8 kHz, (ii) a lateral-to-medial translational component that is visible at frequencies from 2 to greater than 10 kHz, and (iii) a newly described rotational mode around an inferiorly-to-superiorly directed axis that parallels the manubrium of the malleus and dominates ossicular motion between 10 and 16 kHz. This new axis of rotation is located near the posterior edge of the manubrium. The onset of the second rotational mode leads to a boost in the magnitude of sound-induced stapes displacement near 14 kHz, and adds a half-cycle to the accumulating phase in middle-ear sound transmission. Similar measurements in one ear after interruption of the incudostapedial joint suggest the load of the cochlea and stapes annular ligament is important to the presence of the second rotational mode, and acts to limit simple ossicular translation.
Collapse
Affiliation(s)
- John J Rosowski
- Eaton-Peabody Laboratory of Auditory Physiology, Massachusetts Eye and Ear, 243 Charles Street, Boston 02114, MA, USA; Department of Otolaryngology - Head and Neck Surgery, Harvard Medical School, 243 Charles Street, Boston 02114, MA, USA.
| | - Antoine Ramier
- Harvard-MIT Division of Health Sciences and Technology, 77 Massachusetts Avenue, Cambridge 02139 MA, USA; Wellman Center for Photomedicine, Massachusetts General Hospital, 65 Lansdowne St. UP-5, Cambridge 02139, MA, USA
| | - Jeffrey Tao Cheng
- Eaton-Peabody Laboratory of Auditory Physiology, Massachusetts Eye and Ear, 243 Charles Street, Boston 02114, MA, USA; Department of Otolaryngology - Head and Neck Surgery, Harvard Medical School, 243 Charles Street, Boston 02114, MA, USA
| | - Seok-Hyun Yun
- Harvard-MIT Division of Health Sciences and Technology, 77 Massachusetts Avenue, Cambridge 02139 MA, USA; Wellman Center for Photomedicine, Massachusetts General Hospital, 65 Lansdowne St. UP-5, Cambridge 02139, MA, USA
| |
Collapse
|