Lateralization of Interaural Level Differences with Multiple Electrode Stimulation in Bilateral Cochlear-Implant...

Area of Science:

• Audiology
• Neuroscience
• Biomedical Engineering

Background:

• Current bilateral cochlear-implant (BiCI) mapping methods lack standardization for optimizing binaural performance.
• Existing techniques may lead to spatial perceptions inconsistent with the sound's physical origin.
• Investigating intracranial lateralization is crucial for improving auditory spatial awareness in BiCI users.

Purpose of the Study:

• To investigate intracranial lateralization in BiCI users with varying interaural level differences (ILDs).
• To determine an effective method for achieving centered auditory images during multielectrode stimulation.
• To assess if pre-centering single-electrode stimulation improves binaural perception with multielectrode stimulation.

Main Methods:

• Measured lateralization curves in nine BiCI listeners using direct electrical stimulation with a range of ILDs (-20 to +20 CUs).
• Stimuli were delivered via single or multiple electrode pairs at 70-80% of dynamic range.
• A multichannel ILD processing model predicted lateralization for multielectrode stimulation based on single-electrode data.

Main Results:

• BiCI listeners frequently perceived stimulation as non-centered, even at 0 CU ILD.
• Single-electrode stimulation showed significant bias in 44% of cases; multielectrode stimulation showed bias in 25%.
• Centering single-electrode pairs reduced large biases in multielectrode stimulation to 4% (p < 0.001).

Conclusions:

• Current BiCI mapping can create inconsistent spatial perception across electrodes.
• Explicitly centering single-electrode pairs significantly corrects across-electrode perceptual inconsistencies.
• This approach, supported by modeling, may improve binaural abilities like sound localization and speech-in-noise perception.