The relationship between speech perception and electrode discrimination in cochlear implantees

Area of Science:

• Audiology
• Neuroscience
• Biomedical Engineering

Background:

• Speech intelligibility is crucial for cochlear implant (CI) users.
• Understanding how frequency bands affect speech perception in CI users is vital for device optimization.

Purpose of the Study:

• To quantify speech information perception across frequency bands in CI users.
• To compare CI user perception to normal-hearing listeners.
• To investigate the relationship between electrode discrimination and speech perception.

Main Methods:

• Speech Intelligibility Index (SII) procedures were used to assess speech information perception in five frequency bands.
• 15 users of Cochlear Ltd. CI-22M implants and Spectra-22/SPEAK processors participated.
• Electrode discrimination ability was tested using a 4IFC procedure with varying current levels.

Main Results:

• CI users showed significantly reduced speech information in low-to-mid frequencies (170-2680 Hz) compared to normal-hearing listeners.
• A significant correlation was found between electrode discrimination ability and speech information perception in these lower frequencies, especially with loudness variations.
• No such correlation was observed in the high-frequency region (2680-5744 Hz).

Conclusions:

• Speech information in low-to-mid frequencies is more challenging for CI users to perceive.
• Difficulty in discriminating electrode place, particularly with loudness variations, impacts speech perception in these frequency ranges.
• Fine spectral discrimination appears more critical for vowel formants than for higher frequencies in CI users.