Electrophysiologically-based electrode selection has the potential to improve speech perception in cochlear-implant...

Area of Science:

• Neuroscience
• Audiology
• Biomedical Engineering

Background:

• Speech perception in cochlear implant (CI) users varies significantly due to differences in neural modulation encoding along the electrode array.
• Temporal envelope cues are vital for CI speech perception, and deactivating electrodes with poor neural modulation processing has shown potential for improvement.
• Behavioral measures for assessing neural modulation are time-consuming and require active participant feedback, necessitating objective alternatives.

Purpose of the Study:

• To demonstrate the feasibility of measuring 40-Hz electrically-evoked auditory steady-state responses (eASSRs) across multiple CI electrodes using clinical pulse rates.
• To investigate if objective electrode selection based on individual across-array eASSR patterns can enhance speech perception in CI users.
• To correlate eASSR pattern metrics with speech perception performance after accounting for tonotopical effects of electrode deactivation.

Main Methods:

• Recorded 40-Hz eASSRs across the entire CI electrode array using a custom-built EEG system with artifact removal capabilities.
• Developed individualized experimental electrode configurations (MAPs A and B) based on eASSR amplitudes, differentiating electrodes with better versus poorer temporal envelope cue transmission.
• Assessed speech perception in quiet and noise using clinical and experimental MAPs, correlating performance with eASSR patterns.

Main Results:

• Experimental MAP A, selecting electrodes with better temporal envelope encoding based on eASSRs, consistently outperformed MAP B across all listening conditions, though both performed worse than the clinical MAP.
• Higher overall eASSR amplitudes and greater across-array variation were associated with better performance in MAP A, even after controlling for tonotopical effects.
• No significant associations between eASSR patterns and performance were observed for MAP B.

Conclusions:

• Objective electrode selection strategies leveraging local neural modulation encoding, as measured by eASSRs, show promise for optimizing individual CI fitting.
• This approach has the potential to improve speech perception outcomes for cochlear implant recipients by tailoring electrode usage to individual neural processing capabilities.
• Further research into automatic, objective electrode selection based on eASSRs could refine clinical CI fitting protocols.