Mapping auditory nerve firing density using high-level compound action potentials and high-pass noise masking

Area of Science:

• Neuroscience
• Audiology
• Regenerative Medicine

Background:

• Regenerative treatments for sensorineural hearing loss require precise diagnostic tools.
• Current methods like compound action potentials (CAPs) predict auditory nerve survival but lack location specificity.
• Identifying specific neural targets in the cochlea is crucial for effective therapeutic delivery.

Purpose of the Study:

• To investigate if high-level CAPs with a masking paradigm can map auditory nerve firing density across the cochlea.
• To determine normative ranges for CAP-derived neural firing density functions.
• To assess the impact of outer hair cell (OHC) pathology on neural firing distribution.

Main Methods:

• Utilized a high-pass masking paradigm in gerbils.
• Employed broadband chirp and low-frequency toneburst stimuli.
• Measured CAPs at moderate (60 dB pSPL) and high (90 dB pSPL) intensities.

Main Results:

• Neural firing distributions for moderate-intensity chirps were altered by OHC pathology.
• Neural firing distributions for high-level chirps remained unaffected by OHC pathology.
• Established normative ranges for CAP-derived neural firing density functions.

Conclusions:

• CAP-derived neural firing distributions using high-level chirps may offer a reliable estimate of auditory nerve survival.
• This approach appears independent of OHC pathology, enhancing its diagnostic potential.
• Provides a foundation for developing targeted regenerative therapies for hearing loss.