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Published on: December 9, 2022
Mechanisms contributing to central excitability changes during hearing loss.
Nadia Pilati1, Matias J Ison, Matthew Barker
1Department of Cell Physiology and Pharmacology, University of Leicester, Leicester LE19HN, United Kingdom.
Summary
Loud sound exposure causes hearing loss by damaging the cochlea. Early changes in the central auditory pathway, specifically the dorsal cochlear nucleus, show reduced cellular excitability, potentially preventing future tinnitus.
Area of Science:
- Neuroscience
- Auditory Neuroscience
- Cellular Biology
Background:
- Loud sound exposure leads to cochlear damage, hearing loss, and tinnitus.
- Tinnitus is linked to central auditory pathway hyperactivity weeks after noise exposure.
- Early central excitability changes preceding hyperactivity are not well understood.
Purpose of the Study:
- Investigate mechanisms of excitability changes in the dorsal cochlear nucleus (DCN) after loud sound exposure.
- Examine how acoustic overexposure alters synaptic transmission in the DCN.
- Identify early neurobiological markers of hearing loss.
Main Methods:
- Acoustic overexposure in animal models.
- Electrophysiological recordings in the dorsal cochlear nucleus.
- Analysis of synaptic transmission and cellular excitability.
Main Results:
- Reduced myelinated auditory nerve fibers decrease DCN principal cell firing rate.
- Decreased DCN granule cell membrane resistance impacts principal cell firing.
- Inhibitory synaptic transmission is impaired in both auditory and multisensory pathways.
- Cellular excitability decreases in the central auditory pathway.
Conclusions:
- Early cellular mechanisms in the DCN contribute to decreased excitability following hearing loss.
- These changes may serve as early neurobiological markers for hearing loss.
- Understanding these mechanisms could inform interventions for tinnitus prevention.
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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.
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Place theory, or place coding, suggests that different pitches are heard because various sound waves activate specific locations along the cochlea's basilar membrane. The brain determines the pitch of a sound by identifying...
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