Temporal Regularity Detection and Rate Discrimination in Cochlear-Implant Listeners

Abstract

Cochlear implants (CIs) convey fundamental-frequency information using primarily temporal cues. However, temporal pitch perception in CI users is weak and, when measured using rate discrimination tasks, deteriorates markedly as the rate increases beyond 300 pulses-per-second. Rate pitch may be weak because the electrical stimulation of the surviving neural population of the implant recipient may not allow accurate coding of inter-pulse time intervals. If so, this phenomenon should prevent listeners from detecting when a pulse train is physically temporally jittered. Performance in a jitter detection task was compared to that in a rate-pitch discrimination task. Stimuli were delivered using direct stimulation in cochlear implants, on a mid-array and an apical electrode, and at two different rates (100 and 300 pps). Average performance on both tasks was worse at the higher pulse rate and did not depend on electrode. However, there was a large variability across and within listeners that did not correlate between the two tasks, suggesting that rate-pitch judgement and regularity detection are to some extent limited by task-specific processes. Simulations with filtered pulse trains presented to NH listeners yielded broadly similar results, except that, for the rate discrimination task, the difference between performance with 100- and 300-pps base rates was smaller than observed for CI users.

Auditory memory for random time patterns in cochlear implant listeners

“…Overall performance was generally better for Slow rates than Fast rates or Ultra-Fast rates for CI users. This is consistent with previous studies reporting a decrease in performance with increasing rate in various temporal tasks with CI listeners, such as rate discrimination or temporal jitter detection (Gaudrain, Deeks, & Carlyon, 2017;Macherey, Deeks, & Carlyon, 2011;Vandali & van Hoesel, 2012). Thus, it is likely that our observation of a decrease in overall performance with rate can be accounted for by mechanisms independent of the learning process.…”

Discrimination of Voice Pitch and Vocal-Tract Length in Cochlear Implant Users

“…While there is no way to absolutely rule out the possibility that individual differences in cognitive function, for example, due to aging, may have contributed to our pattern of results, it can be argued that this is rather unlikely. Indeed, 3AFC tasks similar to the one used in the present study have been used in other studies where performance of the CI group was found to be equivalent or better than that of the NH group (gap detection in words: Gaudrain et al, Reference Note 2 ; rate pitch discrimination: Gaudrain et al 2017 ). As for age, the NH listeners were on average 22.7 years younger than the CI listeners.…”

“…The perception of temporal pitch is based on the periodicity of the signal or of the temporal envelope of the signal. Temporal pitch perception seems to be relatively preserved in CI listeners, and they demonstrate functional use of this pitch cue similar to that of NH listeners ( Hong & Turner 2009 ; Deroche et al 2014 ; Gaudrain et al 2017 ), as long as F0 remains below 300 Hz ( Shannon 1983 ; Carlyon et al 2002 , 2010 ; Zeng 2002 ). In contrast, place pitch, that is, the pitch that results from exciting different segments of the cochlea, seems to be more difficult to use for CI listeners ( Geurts & Wouters 2001 ; Laneau et al 2004 ), in particular in speech-like stimuli where dynamic spectral envelope fluctuations may interfere with spectral changes induced by F0 differences ( Green et al 2002 , 2004 ).…”

“…This could mean that temporal pitch cues were still sufficiently salient to perform the task at 411 Hz. Single-channel temporal pitch JNDs (based on stimulation rate or on temporal envelope periodicity) reported in the literature range from 3 to 6 st for base rates close to 242 Hz ( McDermott & McKay 1997 ; Zeng 2002 ; Baumann & Nobbe 2004 ; Chatterjee & Peng 2008 ; Carlyon et al 2010 ; Gaudrain et al 2017 ).…”

Pulse-rate discrimination deficit in cochlear implant users: is the upper limit of pitch peripheral or central?

“…Pitch information coded via place of excitation, i.e., differential excitation of the auditory nerve fibers of different characteristic frequencies, is limited (Moore, 2003). CI listeners rely also on temporal processing of the repetition rate of electrical pulses to perceive pitch (Bahmer and Baumann, 2013; Baumann and Nobbe, 2004; Carlyon et al, 2010; Venter and Hanekom, 2014; Gaudrain et al, 2017). Previous studies show that CI listeners are able to identify musical intervals and even recognize melodies by varying the rate of stimulation delivered on a single electrode (Pijl and Schwarz, 1995; McDermott and McKay, 1997).…”