Inner-hair-cell induced hearing loss: A biophysical modeling perspective

Area of Science:

• Auditory Neuroscience
• Computational Biology
• Biophysics

Background:

• Inner hair cell (IHC) and synapse malfunction are key contributors to hearing loss (HL).
• Existing models often lack detailed biophysical simulation of IHCs within a complete auditory pathway.
• Understanding the specific contributions of IHCs and outer hair cells (OHCs) to HL is crucial.

Purpose of the Study:

• To develop a detailed biophysical model of IHCs within an end-to-end computational model of the auditory pathway.
• To simulate different types of hearing loss by altering mechanical and biochemical parameters of IHCs and OHCs.
• To predict human audiometric thresholds and explain common audiogram patterns.

Main Methods:

• Developed a biophysical model of inner-hair cells (IHCs).
• Integrated IHC model into an end-to-end computational model of the auditory pathway.
• Simulated hearing loss by modifying mechanical and biochemical parameters of IHCs and outer hair cells (OHCs).
• Used acoustic signals as input and predicted human audiometric thresholds as output.

Main Results:

• Simulated hearing loss thresholds matched common audiogram patterns.
• OHC damage caused threshold shifts (up to 40 dB) mainly at mid-high frequencies.
• IHC damage affected low and high frequencies differently, with a maximum of 40 dB HL at low frequencies.
• Reduced IHC cilia number led to high-frequency HL up to 120 dB.
• Sloping audiograms were explained by gradual changes in IHC and OHC cilia along the cochlea.

Conclusions:

• The computational model accurately predicts hearing loss audiograms based on hair cell function.
• IHCs play a critical role in determining hearing sensitivity across frequencies, particularly at low frequencies.
• OHC function is more critical for mid-high frequency hearing sensitivity.
• Gradual changes in hair cell cilia number can explain sloping hearing loss patterns.