Evaluating auditory brainstem response to a level-dependent chirp designed based on derived-band latencies.

Area of Science:

• Auditory Neuroscience
• Audiology
• Biomedical Engineering

Background:

• The optimal cochlear-neural delay model for chirp-evoked auditory brainstem responses (ABR) remains undetermined.
• Chirp stimuli aim to improve ABR amplitude by compensating for cochlear traveling wave delays.

Purpose of the Study:

• To establish a level-dependent cochlear-neural delay model.
• To design and evaluate a novel derived-band chirp (DB-Chirp) based on this model.
• To compare the efficacy of the DB-Chirp against a level-specific (LS)-Chirp and a click stimulus in eliciting ABRs.

Main Methods:

• Experiment I: Measured derived-band ABR latencies across different sound levels to estimate cochlear-neural delays.
• Experiment II: Recorded ABRs using a DB-Chirp, an LS-Chirp, and a click stimulus at various normal hearing levels (nHL).
• Analyzed wave I and wave V amplitudes and latencies for statistical significance.

Main Results:

• Cochlear-neural delay increased as sound level decreased, particularly between 0.7 and 5.7 kHz.
• The DB-Chirp elicited significantly larger wave V amplitudes than the LS-Chirp at 45 dB nHL.
• Both chirp stimuli produced significantly larger wave I amplitudes than the click stimulus at specific levels.

Conclusions:

• The developed level-dependent delay model informed the design of an effective DB-Chirp.
• The DB-Chirp shows promise for enhancing ABRs, particularly wave V, at moderate hearing levels.
• This DB-Chirp may be valuable for clinical applications like assessing cochlear synaptopathy and estimating hearing sensitivity.