Effect of changes in mass on middle ear function

SUMMARYThe dimorphic ear of the bullfrog, Rana catesbeiana, has long been enigmatic. The male's tympanic membrane (TM) area approximates twice the area of the female's; however, similar size differences in the area of the columellar footplate were not observed between the sexes. Hence, the male's hearing is expected to be more sensitive than the female's but this is not the case. Asking what offsets the advantage of the large TM, we applied a series of experiments to the auditory system. Male and female audiograms based on stimulation with airborne sound and on both multi-unit responses from the brain and alternating cochlear potentials ('microphonics') showed equal sensitivity and a small difference in frequency response; at low frequencies the male was more sensitive than the female. Amputating the columella and stimulating the stump with mechanical vibration showed that for an equal microphonic response, the male's footplate vibrated with lower amplitude than the female's footplate. Mechanically stimulating the TM of the intact ear replicated this result, excluding the involvement of the mechanical lever. The TM of the male weighs five times the TM of the female, and artificial loading of the TM of either sex greatly reduced the ear's sensitivity. Hence, the male's excessive area ratio (TM to columellar footplate) is offset by the heavier cartilage cushion on the male's TM, damping the TM's response to sound. This is corroborated by experimentally artificially loading the TM. The product of area ratio and footplate vibration amplitude would result in similar stimulation of the inner ear in the two sexes.

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“…The effects of loading R. catesbeiana ears accord in principle with the experience from loading human middle ears (Nishihara et al, 1993).…”

Section: Y L Werner and Otherssupporting

confidence: 52%

Function of the sexually dimorphic ear of the American bullfrog,Rana catesbeiana: brief review and new insight

Werner

Pylka

Schneider

et al. 2009

Journal of Experimental Biology

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“…Thus, the final FE model with all parameters was complete for subsequent model evaluations or mechanical analyses. Finally, experimental results on human or human temporal bone were used to comparatively evaluate the finite element model [7,[12][13][14]. The experimental data from 64 normal human subjects published by Nishihara [13], 10 temporal bones reported by Huber [14] and stapes footplate displacements obtained from 17 human temporal bones by Gan [7] were selected for model evaluation.…”

Section: Resultsmentioning

confidence: 99%

Computer Aided Three-Dimensional Reconstruction and Modeling of Middle Ear Biomechanics by High-Resolution Computed Tomography and Finite Element Analysis

Lee

Chen

Lee

et al. 2006

Biomed. Eng. Appl. Basis Commun.

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In order to present a systematic and practical approach that uses high-resolution computed tomography (HRCT) to derive models of the middle ear for finite element analysis (FEA). This prospective study included 31 subjects with normal hearing and no previous otological disorders. Temporal bone images obtained from 15 right ears and 16 left ears were used for evaluation and reconstruction. High-resolution computed tomography of temporal bone was performed using simultaneous acquisition of 16 sections with a collimated slice thickness of 0.625 mm. All images were transferred to an Amira visualization system for 3D reconstruction. The created 3-D model was translated into two commercial modeling packages, Patran and ANSYS, for finite element analysis. The characteristic dimensions of the model were measured and compared with previous published histological section data. This result confirms that the geometric model created by the proposed method is accurate except the tympanic membrane is thicker than that of histological section method. No obvious difference in the geometrical dimension between right and left ossicles was found (p > 0.05). The 3D model created by finite element method and predicted umbo and stapes displacements are close to the bounds of the experimental curves of Nishihara's, Huber's, and Gan's data across the frequency range of 100-8000 Hz. The model includes a description of the geometry of the middle ear components, and dynamic equations of vibration. The proposed method is quick, practical, low cost and most importantly, non-invasive as compared with histological section methods.

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“…The peak displacement of the center of the footplate averages 10 nm at an 80-dB SPL sound input at the tympanic membrane (TM) for frequencies below 1.0 kHz; this becomes even smaller at higher frequencies [Goode et al, 1989;Nishihara et al, 1993;Hato et al, 2001]. Gundersen and Hogmoen [1976] studied stapes motion with an intact cochlea and found the motion to be piston-like for frequencies below 2.0 kHz; above 2.0 kHz stapes motion became complex.…”

Section: Introductionmentioning

confidence: 99%

Three-Dimensional Stapes Footplate Motion in Human Temporal Bones

Hato

Stenfelt²,

Goode³

2003

Audiol Neurotol

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122

117

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The literature provides conflicting information on whether the motion of the stapes footplate is piston-like or some other type of motion, such as rotational or rocking. Examination of the three-dimensional (3D) motion of the stapes footplate appears to be an excellent way to understand this complicated motion. Five microsphere reflective targets were placed on the stapes footplate in ten fresh human cadaver temporal bone preparations, and their vibration measured through an extended facial recess approach using a laser Doppler vibrometer. The five target sites on the stapes footplate were center, anterior, posterior, superior and inferior. The stimulus was a sound input of 80–120 dB SPL at the tympanic membrane over a frequency range of 0.1 to 10 kHz. The 3D motion of the stapes footplate was calculated using the velocity amplitude and phase obtained for each target. For frequencies up to 1.0 kHz the vibration of the stapes footplate was primarily piston-like; this motion became complex at higher frequencies, with rotary motion along both the long and short axis of the footplate. When the cochlea was drained, stapes footplate motion became essentially piston-like for all frequencies.

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Effect of changes in mass on middle ear function

Cited by 82 publications

References 13 publications

Function of the sexually dimorphic ear of the American bullfrog,Rana catesbeiana: brief review and new insight

Function of the sexually dimorphic ear of the American bullfrog,Rana catesbeiana: brief review and new insight

Computer Aided Three-Dimensional Reconstruction and Modeling of Middle Ear Biomechanics by High-Resolution Computed Tomography and Finite Element Analysis

Three-Dimensional Stapes Footplate Motion in Human Temporal Bones

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