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Feed-forward and feed-backward amplification model from cochlear cytoarchitecture: an interspecies comparison
Yong-Jin Yoon1, Charles R Steele, Sunil Puria
1Department of Mechanical Engineering, Stanford University, Stanford, California, USA.
Biophysical Journal
|December 31, 2010
Summary
Mammalian hearing
Area of Science:
- Auditory Neuroscience
- Biophysics
- Computational Biology
Background:
- Mammalian hearing's sensitivity and bandwidth rely on outer hair cell (OHC) motility.
- OHC somatic and hair-bundle movements are crucial for the cochlear amplifier mechanism.
Purpose of the Study:
- To develop and validate a biophysical model of the mammalian cochlea.
- To investigate the role of OHC motility in cochlear amplification and frequency tuning.
Main Methods:
- A 3D biophysical cochlear fluid model was created for gerbil, chinchilla, cat, and human.
- An active "push-pull" cochlear amplifier mechanism was incorporated.
- The time-averaged Lagrangian method was employed for simulations.
Main Results:
- Simulated basilar membrane (BM) velocity (V(BM)) matched in vivo measurements for gerbils and chinchillas.
- Mechanical tuning curves based on constant V(BM) better predicted neural tuning thresholds than constant displacement.
- Simulated Q₁₀ values aligned with neural tuning and BM width across species.
Conclusions:
- The model supports the hypothesis of an active cochlear amplifier driven by OHCs.
- Inner hair cell sensitivity to V(BM) is suggested over BM displacement.
- BM width is a potential factor influencing cochlear tuning sharpness (Q₁₀).
Related Concept Videos
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.
01:22Hair 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.
01:15Auditory 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...
01:07Cell Signaling Feedback Loops
Positive and negative feedback loops are crucial for regulating biological signaling systems. These feedback loops are processes that connect output signals to their inputs.
Negative feedback loops
Most signaling systems have negative feedback loops that can perform different functions such as output limiter, and adaptation.
Output limiter
Upon receiving an input signal, the cellular response rapidly increases until a threshold is reached. Beyond this threshold, a negative feedback loop...
Negative feedback loops
Most signaling systems have negative feedback loops that can perform different functions such as output limiter, and adaptation.
Output limiter
Upon receiving an input signal, the cellular response rapidly increases until a threshold is reached. Beyond this threshold, a negative feedback loop...
01:24Effects of feedback
Feedback in control systems plays a critical role in shaping various operational parameters, extending beyond simple error reduction to influence stability, bandwidth, gain, impedance, and sensitivity. Understanding these effects requires examining a basic feedback system characterized by defined input, output, error, and feedback signals.
Feedback significantly modifies the gain of a control system. The gain of a system without feedback is altered by a factor of one plus GH, where G represents...
Feedback significantly modifies the gain of a control system. The gain of a system without feedback is altered by a factor of one plus GH, where G represents...