The relationship between channel interaction, electrode placement, and speech perception in adult cochlear implant users.

This study (1) characterized the effects of channel interaction using spectral blurring, (2) evaluated an image-guided electrode selection (IGES) method aiming to reduce channel interaction, and (3) investigated the impact of electrode placement factors on the change in performance by condition. Twelve adult MED-EL (Innsbruck, Austria) cochlear implant recipients participated. Performance was compared across six conditions: baseline (no blurring), all blurred, apical blurred, middle blurred, basal blurred, and IGES. Electrode placement information was calculated from post-insertion computerized tomography (CT) imaging. Each condition tested measures of speech recognition and subjective ratings. Results showed poorer performance when spectral blurring was applied to all channels compared to baseline, suggesting an increase in channel interaction was achieved. Vowel recognition was more sensitive to apical and middle blurring while consonant recognition was more sensitive to basal blurring, indicating that phoneme identification may be useful for assessing channel interaction clinically. IGES did not significantly improve group performance, and electrode placement factors did not impact results. However, participants who were more affected by spectral blurring tended to benefit more from IGES. These findings indicate that spectral blurring can help identify areas most affected by channel interaction to help optimize electrode selection.