Perceptual learning of pitch provided by cochlear implant stimulation rate

Abstract

Cochlear implant users hear pitch evoked by stimulation rate, but discrimination diminishes for rates above 300 Hz. This upper limit on rate pitch is surprising given the remarkable and specialized ability of the auditory nerve to respond synchronously to stimulation rates at least as high as 3 kHz and arguably as high as 10 kHz. Sensitivity to stimulation rate as a pitch cue varies widely across cochlear implant users and can be improved with training. The present study examines individual differences and perceptual learning of stimulation rate as a cue for pitch ranking. Adult cochlear implant users participated in electrode psychophysics that involved testing once per week for three weeks. Stimulation pulse rate discrimination was measured in bipolar and monopolar configurations for apical and basal electrodes. Base stimulation rates between 100 and 800 Hz were examined. Individual differences were quantified using psychophysically derived metrics of spatial tuning and temporal integration. This study examined distribution of measures across subjects, predictive power of psychophysically derived metrics of spatial tuning and temporal integration, and the effect of training on rate discrimination thresholds. Psychophysical metrics of spatial tuning and temporal integration were not predictive of stimulation rate discrimination, but discrimination thresholds improved at lower frequencies with training. Since most clinical devices do not use variable stimulation rates, it is unknown to what extent recipients may learn to use stimulation rate cues if provided in a clear and consistent manner.

Cochlear-implant listeners benefit from training with time-compressed speech, even at advanced ages

“…Similar to previous research, the present study tested listeners at multiple sessions and evaluated performance over time ( Goldsworthy and Shannon, 2014 ; Bissmeyer et al , 2020 ). For the current study, a control group was not included.…”

“…The current study is an initial effort to evaluate the benefit of an adaptive training paradigm with time-compressed speech for adult CI listeners across the lifespan. We hypothesized that listeners would demonstrate improved recognition of rapid speech after completion of auditory training, based on previous studies showing improved pulse-rate discrimination following training ( Goldsworthy and Shannon, 2014 ; Bissmeyer et al , 2020 ; Anderson et al , 2022 ). Although older CI listeners were expected to demonstrate improved recognition of rapid speech following training, it was also hypothesized that the training gains would diminish with increasing age (i.e., there would be an age by training interaction resulting in more modest training gains for older listeners).…”

Computational Modeling of Synchrony in the Auditory Nerve in Response to Acoustic and Electric Stimulation

“…The spatial response to the harmonic tone is nearly identical for the three strategies, with the response quantified as the proportion of charge delivered to each electrode. Note that proportional charge is normalized here, clinical implementation of PDT will likely require higher charge on low-frequency channels since lower pulse rates require more charge per pulse to obtain audibility thresholds and comfortable listening levels (Goldsworthy and Shannon, 2014;Bissmeyer et al, 2020;Goldsworthy et al, 2021Goldsworthy et al, , 2022. For all three stimulation strategies, the fundamental frequency clearly produces a resolved peak in the spatial pattern, which occurs in the stimulation pattern as well as after modeling current spread and neural excitation.…”

Development and Characterization of a Micromagnetic Alternative to Cochlear Implant Electrode Arrays

“…The source signal is a modulated sinusoidal current. A low-frequency, 5 kHz, signal will be pulsed on and off at a frequency of 800 Hz with a duty cycle of 50% because, though general human temporal modulation sensitivity is approximately 300 Hz [28], many CI users can identify differences in hearing with stimulation frequencies up to 800 Hz [29]. The observation region will experience a change of magnetic field over time, creating an induced electric field on the tissue plane, resulting in the eddy current described above.…”