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Updated: May 23, 2026
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Published on: April 21, 2022
Reverse transmission along the ossicular chain in gerbil
Wei Dong1, Willem F Decraemer, Elizabeth S Olson
1Department of Otolaryngology, Head and Neck Surgery, Columbia University, 630 West 168th Street, New York, NY 10032, USA. wd2015@columbia.edu
Summary
Distortion product otoacoustic emissions travel backward from the cochlea. Reverse middle ear transmission shows amplitude loss compared to forward transmission, likely due to differing load impedances.
Area of Science:
- Auditory Neuroscience
- Bioacoustics
- Otoacoustic Emissions
Background:
- The cochlea generates combination tones via its active process and nonlinearity when stimulated by two primary tones.
- These distortion tones propagate in reverse through the middle ear and can be measured as distortion product otoacoustic emissions (DPOAEs) in the ear canal (EC).
- Understanding reverse middle ear transmission is crucial for interpreting DPOAE measurements.
Purpose of the Study:
- To compare middle ear transmission in the reverse direction (ear canal to cochlea) with forward transmission (cochlea to ear canal).
- To evaluate ossicular velocity and ear canal pressure responses at distortion product frequencies.
- To investigate the influence of load impedances on forward and reverse middle ear transmission.
Main Methods:
- Gerbil ears were stimulated with two equal-intensity tones at fixed frequency ratios (f(2)/f(1) = 1.05 or 1.25).
- Middle ear ossicular motion was measured using a laser interferometer via access through the pars flaccida.
- Ossicular velocity was referenced to ear canal pressure to assess reverse transmission.
Main Results:
- Reverse middle ear transmission exhibited an additional amplitude loss when referenced to ear canal pressure, compared to the gain observed in forward transmission.
- Sound transmission along the ossicular chain itself showed similar characteristics in both forward and reverse directions.
- The observed differences in overall middle ear transmission are attributed to variations in load impedance (cochlea for forward, ear canal for reverse).
Conclusions:
- Reverse middle ear transmission is characterized by amplitude loss relative to ear canal pressure.
- The ossicular chain's transmission properties are largely symmetrical in forward and reverse directions.
- Load impedance differences are the primary factor explaining the asymmetry in forward versus reverse middle ear transmission.
Related Concept Videos
01:11The Auditory Ossicles
The auditory ossicles of the middle ear transmit sounds from the air as vibrations to the fluid-filled cochlea. The auditory ossicles consist of two malleus (hammer) bones, two incus (anvil) bones, and two stapes (stirrups), one on each side. These bones develop during the fetal stage and are the ones to ossify first. They are fully mature at birth and do not grow afterward.
The aptly named stapes look very much like a stirrup. The three ossicles are unique to mammals, and each plays a role in...
The aptly named stapes look very much like a stirrup. The three ossicles are unique to mammals, and each plays a role in...
01:13The Cochlea
The cochlea is a coiled structure in the inner ear that contains hair cells—the sensory receptors of the auditory system. Sound waves are transmitted to the cochlea by small bones attached to the eardrum called the ossicles, which vibrate the oval window that leads to the inner ear. This causes fluid in the chambers of the cochlea to move, vibrating the basilar membrane.
01:16Anatomy of the Ear
Auditory sensation, commonly called hearing, involves the transformation of sonic waves into neural impulses facilitated by the structures of the auditory organ. The prominent, flesh-like structure on the side of the head, called the auricle, directs sound waves towards the auditory canal. The auricle is often mislabeled as the pinna, a term more aligned with mobile structures like a feline's external ear. The auditory canal penetrates the cranium via the external auditory meatus of the...