Do cochlear implant users experience the same amplitude modulation rates in each ear?

Abstract

Cochlear implant (CI) users often produce different vocal fundamental frequencies (F0s) when using the left versus the right CI device. Since pitch perception and production are linked, differences in produced F0s likely indicate differences in perceived vocal pitches for the same F0 when using different ears. One possible explanation for different pitch perceptions with each ear is that, while F0s are typically encoded in the amplitude modulations (AM) of electrical stimulation, the resulting temporal pitch may differ for each ear. This study aimed to investigate if CI users perceive the same AM rates as different pitches with each ear. Five CI users participated in an AM pitch matching study using place-pitch-matched electrodes in the two ears. They were given two sounds with AM and asked to turn a dial, changing the AM rate in one ear to make the pitch of the second sound similar to the pitch of the first sound. The preliminary results showed that some participants perceived different pitches in the two ears for the same AM rate, and some did not, suggesting that the same AM-encoded F0s may be perceived as a different vocal pitch, but only for some CI users.