Effects of the electrode location on tonal discrimination and speech perception of Mandarin-speaking patients with a cochlear implant.

OBJECTIVES/HYPOTHESIS: This study assessed the effects of varying the electrode location on tonal discrimination and speech perception in Mandarin Chinese-speaking patients.

STUDY DESIGN

A controlled study with six experimental conditions.

METHODS

Seven Mandarin-speaking listeners who received a MED-EL cochlear implant (CI), ranging in age from 12.88 to 36.43 years (mean, 25.51 years), with an average of 5.28 years of device experience, participated this study. To evaluate the effects of electrode location, six experimental conditions each with the switch off at six different electrodes were designed. Identification tests of Mandarin lexical tones and words were performed.

RESULTS

Among experimental conditions with electrode lengths of 31, 23.8, and 16.6 mm, the CI subjects exhibited improved vowel and consonant identification in the condition of 31 mm, reflecting the apical location of electrodes. Specifically, the improvement was observed in the identification score for the vowel backness and height, as well as for the consonant place of articulation. Comparison among three settings with a same electrode length of 12.6 mm and the setting with stimulation to the midregion of the cochlea produces better words as well as the vowel and consonant identification compared with stimulation to basal and apical regions. However, no significant difference was observed for the lexical tone identification among conditions with different electrode location and stimulating region.

CONCLUSIONS

Less mismatch of the frequency-to-place alignment may account for the improvement of word identification in conditions with electrodes coverage to more apical location; and in conditions where the mid-region of the cochlea were stimulated.