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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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Use of non-invasive measures to predict cochlear synapse counts
Naomi F Bramhall1, Garnett P McMillan1, Sharon G Kujawa2
1VA RR&D National Center for Rehabilitative Auditory Research (NCRAR), VA Portland Health Care System, Portland, OR, 97239, USA; Department of Otolaryngology/Head & Neck Surgery, Oregon Health & Science University, Portland, OR, 97239, USA.
Hearing Research
|October 27, 2018
Summary
Cochlear synaptopathy, a hidden cause of hearing loss, can be detected non-invasively. Combining auditory brainstem response (ABR) and distortion product otoacoustic emission (DPOAE) tests predicts inner hair cell synapse loss.
Area of Science:
- Auditory Neuroscience
- Otoacoustic Emissions
- Sensorineural Hearing Loss
Background:
- Cochlear synaptopathy, the loss of synapses between inner hair cells and auditory nerve fibers, is implicated in aging, noise, and drug-induced hearing loss.
- This synaptic damage can precede measurable hearing threshold changes, making it undetectable with standard audiograms.
- Current diagnostic methods cannot directly confirm cochlear synaptic loss in living humans.
Purpose of the Study:
- To develop and validate a non-invasive method for diagnosing cochlear synaptopathy in humans.
- To establish a predictive model for estimating synaptic counts using auditory brainstem response (ABR) and distortion product otoacoustic emission (DPOAE) measurements.
Main Methods:
- Utilized an age-graded series of mice to model cochlear synaptopathy.
- Employed partial least squares regression to model structure-function relationships between physiological measures and synaptic counts.
- Combined auditory brainstem response (ABR) and distortion product otoacoustic emission (DPOAE) measurements.
Main Results:
- The combined ABR and DPOAE model accurately predicted synaptic ribbon counts per inner hair cell (IHC) within 1-2 synapses across various cochlear frequencies in aging mice.
- The model showed potential limitations, overpredicting synapse counts in noise-exposed mice, suggesting different damage patterns between aging and noise-induced synaptopathy.
Conclusions:
- A non-invasive approach combining ABR and DPOAE shows promise for identifying synaptic/neuronal loss in the cochlea.
- Further research is needed to refine the model for different types of acquired hearing loss, such as noise-induced damage.
Keywords:
Auditory brainstem responseCochlear synaptopathyHidden hearing lossLeast-squares analysisNoise-induced hearing lossOtoacoustic emissionsMore Related Videos
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