Loudness growth functions and EABR characteristics in Digisonic cochlear implantees

Area of Science:

• Audiology
• Neuroscience
• Biomedical Engineering

Background:

• Cochlear implants (CIs) aim to restore hearing by electrically stimulating the auditory nerve.
• Understanding loudness perception is crucial for optimizing CI programming.
• Electrically evoked auditory brainstem responses (EABRs) offer an objective measure of neural activity.

Purpose of the Study:

• To investigate the relationship between EABRs and subjective loudness perception at different stimulation rates in CI users.
• To explore the utility of EABRs in predicting loudness perception limits for CI programming.

Main Methods:

• Measured EABRs and loudness functions using categorical loudness scaling in 14 subjects with MXM Digisonic cochlear implants.
• Stimulation involved 75-Hz and 300-Hz pulse trains delivered to the apical electrode.
• Correlated EABR wave V thresholds with perceptual thresholds and analyzed EABR saturation levels.

Main Results:

• Loudness functions differed significantly between 75 Hz and 300 Hz, with steeper growth at 300 Hz.
• Significant correlations were found between EABR wave V thresholds and perceptual thresholds at both rates.
• EABR wave V saturation occurred at levels corresponding to 'Too loud' (300 Hz) or 'Comfortable' (75 Hz) loudness.

Conclusions:

• Stimulation rate significantly impacts loudness perception in cochlear implant users.
• EABR measures, particularly wave V saturation, show potential for estimating perceptual dynamic range limits.
• Further research is needed to reliably predict maximum comfort levels from EABRs for individual CI users.