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Updated: Jul 11, 2026
10:53
Optogenetic Stimulation of the Auditory Nerve
Published on: October 8, 2014
Ca2+ current-driven nonlinear amplification by the mammalian cochlea in vitro
1Laboratory of Sensory Neuroscience and Howard Hughes Medical Institute, The Rockefeller University, 1230 York Avenue, New York, New York 10021, USA.
Nature Neuroscience
|January 12, 2005
Summary
The inner ear uses an active process to improve hearing sensitivity and frequency selectivity. This study suggests calcium currents drive this process, supporting active hair-bundle movement as the mechanism for cochlear amplification.
Area of Science:
- Auditory Neuroscience
- Mechanobiology
- Inner Ear Physiology
Background:
- Hearing sensitivity and frequency selectivity rely on an active process in the inner ear.
- Two proposed mechanisms are receptor potential-based electromotility and Ca(2+)-driven hair-bundle motility.
Purpose of the Study:
- To investigate the cellular mechanisms of the cochlear amplifier.
- To link the cochlear amplifier's phenomenology to cellular processes using an in vitro model.
Main Methods:
- Developed an in vitro cochlear preparation from Meriones unguiculatus for optical access.
- Used acoustic and electrical stimulation to assess cochlear function.
- Blocked transduction with amiloride and manipulated Ca(2+) currents to isolate mechanisms.
Main Results:
- Demonstrated intact forward and reverse mechanotransduction in the preparation.
- Observed hair bundle resonance and nonlinear amplification characteristic of the active process.
- Found that blocking transduction abolished nonlinear amplification, while preserving Ca(2+) currents did not.
Conclusions:
- The Ca(2+) current is the primary driver of the cochlear active process.
- Active hair-bundle motility is supported as the mechanism underlying cochlear amplification.
Related Concept Videos
01:22Hair Cells
Hair cells are the sensory receptors of the auditory system—they transduce mechanical sound waves into electrical energy that the nervous system can understand. Hair cells are located in the organ of Corti within the cochlea of the inner ear, between the basilar and tectorial membranes. The actual sensory receptors are called inner hair cells. The outer hair cells serve other functions, such as sound amplification in the cochlea, and are not discussed in detail here.
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.
01:15Auditory Pathway
Auditory pathways constitute the complex neural circuits responsible for transmitting and interpreting auditory information from the peripheral auditory system to the brain. Sound waves are initially captured by the outer ear, funneled through the ear canal, and reach the tympanic membrane (eardrum). These vibrations are transmitted via the middle ear's ossicles to the inner ear's cochlea.
When viewed cross-sectionally, the cochlea reveals the scala vestibuli and scala tympani flanking the...
When viewed cross-sectionally, the cochlea reveals the scala vestibuli and scala tympani flanking the...