Electric pitch perception with cochlear implants: Using real-life sounds to get back on the right track

Authors: Floris Rotteveel 1*; Bert Maat 1; Chris James 2; Damir Kovačić 3,  Deniz Başkent 1; Etienne Gaudrain4

1University Medical Center Groningen
2 Cochlear France SAS
3 Department of Physics, Faculty of Science, University of Split
4 Lyon Neuroscience Research Center, Université Lyon 1, Université de Saint-Etienne

Pitch perception is an essential element of human communication, which is hindered in cochlear implant (CI) users. Past studies with more artificial stimuli, such as single-channel pulse trains, have suggested that pitch perception via a CI relies primarily on temporal cues as opposed to via normal hearing (NH) that relies heavily on spectral cues. However, recent studies involving more realistic stimuli suggest that implant users might also be utilizing spectral cues in addition to the temporal cues. Here, we aim to clarify the relative contributions of spectral and temporal cues to pitch perception of CI users using realistic speech stimuli, such as syllables, words, and short sentences.

Stimuli will be generated by manipulating the F0 of Dutch syllables, words, and short sentences. We will assess the prevalence of both cues in the stimuli by recording the output of implant-in-a-box’s from Cochlear Ltd and Advanced Bionics. The pitch cues of these recordings are then manipulated to create four types of speech stimuli: unaltered, or spectral, temporal, or both cues removed. Using a research interface, the manipulated recordings will be presented to CI participants. F0 pitch discrimination abilities will then be assessed with adaptive alternative-forced choice (AFC) tasks which yield F0 just-noticeable differences (JNDs) and psychometric functions.

Results and Conclusions
With this method we will systematically inspect the role of both cues across parameters concerning the nature of the stimuli and implant stimulation strategy. Our expectations for the results are: 1) F0 JNDs will increase with decreasing pitch cue availability. 2) When all cues are removed, CI users will be unable to converge to a JND. 3) The relative contributions of spectral and temporal cues depends on the content of the stimulus as well as the stimulation strategy. The findings will clarify which type of cue should be enhanced to improve pitch perception of CI users.