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Immunolabeling and Counting Ribbon Synapses in Young Adult and Aged Gerbil Cochleae
Published on: April 21, 2022
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Cochlear aging disrupts the correlation between spontaneous rate- and sound-level coding in auditory nerve fibers
Amarins N Heeringa1,2, Fiona Teske2, Go Ashida1,2
1Cluster of Excellence "Hearing4all," Department of Neuroscience, School of Medicine and Health Science, Carl von Ossietzky University Oldenburg, Oldenburg, Germany.
Journal of Neurophysiology
|August 16, 2023
Summary
Aging alters auditory nerve fiber function, impacting how the brain perceives sound. These age-related changes in auditory nerve fibers (ANFs) affect spontaneous rates and sensitivity, blurring established classifications.
Area of Science:
- Neuroscience
- Auditory Physiology
- Gerontology
Background:
- Auditory nerve fibers (ANFs) transmit acoustic information from the cochlea to the brain.
- Aging causes cochlear degeneration, affecting sensory hair cells and stria vascularis.
- Understanding age-related changes in ANF function is crucial for auditory health.
Purpose of the Study:
- To investigate the functional effects of age-related cochlear pathologies on ANF spiking activity.
- To characterize changes in sensitivity and spontaneous rates (SRs) of ANFs in aged gerbils.
- To model the impact of cochlear degeneration on ANF physiology and rate-level functions (RLFs).
Main Methods:
- Recorded rate-level functions (RLFs) from ANFs of young and aged Mongolian gerbils.
- Classified RLFs into flat-saturating, sloping-saturating, and straight categories.
- Utilized a physiologically based cochlear model to simulate degeneration effects.
Main Results:
- Aged gerbils showed lower SR in low-frequency ANFs and loss of low-SR fibers in high-frequency ANFs.
- The distribution of RLF types shifted in low-SR fibers of aged gerbils.
- Modeled degeneration affecting basilar membrane gain explained altered RLF types and decreased sensitivity.
Conclusions:
- Age-related changes in ANF characteristics blur established relationships between SR and RLF types.
- Decreased sensitivity and altered SR distributions in aged gerbils impact auditory nerve coding.
- These findings highlight significant age-dependent alterations in auditory information processing.
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