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Updated: Sep 15, 2025
09:54
Morphological and Functional Evaluation of Ribbon Synapses at Specific Frequency Regions of the Mouse Cochlea
Published on: May 10, 2019
12.1K
Amplification through local critical behavior in the mammalian cochlea
Rodrigo G Alonso1,2, Francesco Gianoli2, Brian Fabella1,2
1HHMI, The Rockefeller University, New York, NY 10065.
Summary
Mammalian hearing relies on an active process with four key features. This study shows that the mammalian cochlea, like in frogs, uses a Hopf bifurcation near criticality to achieve these auditory properties.
Area of Science:
- Auditory Neuroscience
- Biophysics
- Mammalian Physiology
Background:
- Hearing involves an active process enhancing mechanical input detection.
- This process exhibits amplification, sharp frequency tuning, compressive nonlinearity, and otoacoustic emissions.
- In nonmammals, this is seen in individual hair cells near a Hopf bifurcation; in mammals, it's attributed to outer hair cells and traveling waves, with mechanisms debated.
Purpose of the Study:
- To investigate the cellular mechanisms of the mammalian auditory active process.
- To determine if criticality and Hopf bifurcations play a role in mammalian hearing.
- To explore the unified biophysical principles of auditory processing across species.
Main Methods:
- Studied ex vivo mammalian cochlea segments in a simulated in vivo environment.
- Recorded auditory responses to analyze amplification, frequency tuning, and nonlinearity.
- Investigated the role of criticality and Hopf bifurcations in the active process.
Main Results:
- The ex vivo mammalian cochlea demonstrated the active process features: amplification, frequency tuning, compressive nonlinearity, and distortion product generation.
- The active process was found to operate locally, independent of traveling waves.
- The sensory epithelium achieves active amplification by operating near criticality at a Hopf bifurcation.
Conclusions:
- Mammalian auditory processing shares a unified biophysical principle with nonmammals, operating near criticality at a Hopf bifurcation.
- This finding resolves debates about cellular mechanisms in mammalian hearing.
- The study reveals a fundamental mechanism underlying auditory processing across diverse species.
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