Biology subjects

Tubelli, A.

Publications and source records attributed to Tubelli, A..

4 recordsLinked to original sources

bioRxiv2026

Sound-Driven Motion of Human Cochlear Structures Depends on Organ of Corti Integrity

Optical coherence tomography (OCT) was used to image and measure the passive sound-driven displacements of cochlear structures in situ through the intact round window membrane of fresh human cadaveric specimens at 12 to 30 hours postmortem. We find that the anatomical integrity of the organ of Corti (OoC) affects cochlear structural motion. OoC with high integrity (erect with supporting cells) have small osseous spiral lamina (OSL) motion. Conversely, OoC with low integrity (flattened without supporting cells) have large OSL motion. For the ratio of motion between the basilar membrane (BM) and OSL (BM/OSL), OoC with high integrity has large BM/OSL motion while a cochlear partition without OoC has small BM/OSL motion. Furthermore, the high-integrity OoC has reticular lamina surface motion that is lower than the BM, whereas low-integrity OoC has similar reticular lamina and BM motion. This relationship between OoC anatomical integrity and cochlear structural motion will have consequential effects on sound transduction.

neuroscience↗

bioRxiv2026

A nonlinear time-domain finite-element model of the human middle ear subjected to intense sound waves

Computational models of the middle ear are typically developed within the linear range of the middle ear's response, which corresponds to typical sounds in daily life. Understanding middle-ear biomechanics under high-intensity sounds is also important for assessing potential auditory damage under adverse conditions. In this study, a finite-element (FE) model of the human middle ear plus the external ear canal is presented, employing a first-order Ogden hyperelastic material formulation and time-domain nonlinear analysis to capture nonlinear deformation of soft tissues and the resulting middle-ear response. The model was analyzed using pure-tone pressure excitations applied at the ear canal entrance over the 80 Hz to 8 kHz frequency range and 110 to 180 dB sound pressure levels (SPL). The ear canal pressure near the tympanic membrane (TM) and full-field three-dimensional response of the middle ear structures were examined. Across the investigated frequency range, the simulated middle-ear motion exhibited a transition from predominantly piston-like behavior at low frequencies, up to 1 kHz, to increasingly intricate multi-modal and multi-directional vibration patterns at higher frequencies. Nonlinear behaviors became increasingly significant at high frequencies and high stimulus levels, including compressive/expansive pressure-displacement relationships, waveform distortions, and the emergence of non-harmonic spectral components. The model developed in this study provides a computational framework for studying nonlinear sound transmission through the middle ear and its implications for high-intensity acoustic exposure. The findings contribute to a better understanding of middle-ear mechanics under adverse conditions and support future investigations of acoustic trauma and hearing protection strategies.

bioengineering↗

bioRxiv2024

Computational model of the human cochlea with motion of the layered osseous spiral lamina

PurposeIn the base of the human cochlea, the partition anatomy is distinct from the commonly recognized anatomy of laboratory animals. The human features a radially wide, osseous spiral lamina (OSL) and a soft-tissue bridge region that connects the OSL to the basilar membrane proper. In addition to the basilar membrane, the human OSL and bridge move considerably. We investigated the complex cochlear partition in human emphasizing the layered structure of the OSL with a finite element model. Model results were calibrated with experimental measurements of motion from optical coherence tomography. MethodsThe box model contained two fluid chambers separated by a cochlear partition and a helicotrema. Model geometrical and material properties either came from literature, measurements, or were tuned to produce a frequency-place map for the passive human cochlea as well as motion results similar to experimental measurements. ResultsThe model motion results of the cochlear partition were similar to experimental results mostly within 5 dB but with differences at the high frequencies in both magnitude and phase beyond the best frequency. Around the best frequency location, the radial profile of cochlear partition motion was generally similar in both shape and magnitude. Sensitivity analysis, changing material-property parameters of the middle layer where the cochlear nerve fibers run between the layers of OSL plates, produced small changes in the model response and also showed negligible stress compared to the outer OSL plates. ConclusionThese results suggest that the layered OSL anatomy is favorable as a conduit and protection for the nerve fibers while simultaneously functioning as a mechanical lever.

biophysics↗

bioRxiv2022

A Cochlea-Slice Model using Floquet Boundary Conditions shows Global Tuning

A common assumption about the cochlea is that the local characteristic frequency (CF) is determined by a local resonance of basilar-membrane (BM) stiffness with the mass of the organ-of-Corti (OoC) and entrained fluid. We modeled the cochlea while avoiding such a priori assumptions by using a finite-element model of a 20-m-thick cross-sectional slice of the middle turn of a passive gerbil cochlea. The model had anatomically accurate structural details with physiologically appropriate material properties and interactions between the fluid spaces and solid OoC structures. The longitudinally-facing sides of the slice had a phase difference that mimicked the traveling-wave wavelength at the location of the slice by using Floquet boundary conditions. A paired volume-velocity drive was applied in the scalae at the top and bottom of the slice with the amplitudes adjusted to mimic experimental BM motion. The development of this computationally efficient model with detailed anatomical structures is a key innovation of this work. The resulting OoC motion was greatest in the transverse direction, stereocilia-tip deflections were greatest in the radial direction and longitudinal motion was small in OoC tissue but became large in the sulcus at high frequencies. If the source velocity and wavelength were held constant across frequency, the OoC motion was almost flat across frequency, i.e., the slice showed no local resonance. A model with the source velocity held constant and the wavelength varied realistically across frequency, produced a low-pass frequency response. These results indicate that tuning in the gerbil middle turn is not produced by a resonance due to local OoC mechanical properties, but rather is produced by the characteristics of the traveling wave, manifested in the driving pressure and wavelength. STATEMENT OF SIGNIFICANCEThe sensory epithelium of hearing, the organ of Corti, is encased in the bone of the fluid-filled cochlea and is difficult to study experimentally. We provide a new method to study the cochlea: making an anatomically-detailed finite-element model of a small transverse slice of the cochlea using Floquet boundary conditions and incorporating global cochlear properties in the slice drive and the wavelength-frequency relationship. The model shows that the slice properties do not show a mechanical resonance and therefore do not produce the frequency-response tuning of the cochlea. Instead, tuning emerges from global cochlear properties carried by the traveling wave.

biophysics↗