Influence of the frequency-to-electrode mapping on the pitch discrimination in Cochlear Implant users

Introduction:

For many Cochlear Implant (CI) users the perception of music is still challenging. The limited frequency resolution might be the dominating reason for the unsatisfying musical enjoyment. In this study, the frequency discrimination within various CI electrodes was investigated psychophysically.

Methods:

12 CI users and 7 normal hearing control subjects participated in a prospective study. In the first part, sinusoidal tone pairs were presented. The task was to decide whether the pitch was same or different. The discrimination of intervals in respect to the absolute position of the frequencies in respect to the band filter limits was calculated and compared to the respective hit rates. In the second part, melodies were presented in two different keys excluding their rhythm cues and lyrics. The task was to identify the songs with the help of a closed response list. The hit rates for both keys were compared in order to determine a possible influence of the pitch shift on the hit rate.

Results:

On average, CI-users could discriminate 60, 4% of the intervals, the normal hearing subjects 96,4%. The hit rates in the basal electrodes were better than in the apical regions. The position of intervals relative to the electrode border influenced the hit rate.

The CI users identified the melodies significantly worse (33%) than the normal hearing subjects (99%). There is no significant difference in the hit rate between the two keys.

Conclusions:

The ability of discrimination of intervals in respect to their position leads to hypotheses for the improvement of the frequency-to-electrode mapping in cochlear implants.

Publication History

Publication Date:
18 April 2018 (online)