Vowel and consonant confusions from spectrally manipulated stimuli designed to simulate poor cochlear implant electrode-neuron interfaces.

Mishaela Dinino,Matthew B Winn,Julie Arenberg Bierer,Richard A Wright

doi:10.1121/1.4971420

Mishaela Dinino, Matthew B Winn + Show 2 more

Open Access

https://doi.org/10.1121/1.4971420

Copy DOI

Abstract

Suboptimal interfaces between cochlear implant (CI) electrodes and auditory neurons result in a loss or distortion of spectral information in specific frequency regions, which likely decreases CI users' speech identification performance. This study exploited speech acoustics to model regions of distorted CI frequency transmission to determine the perceptual consequences of suboptimal electrode-neuron interfaces. Normal hearing adults identified naturally spoken vowels and consonants after spectral information was manipulated through a noiseband vocoder: either (1) low-, middle-, or high-frequency regions of information were removed by zeroing the corresponding channel outputs, or (2) the same regions were distorted by splitting filter outputs to neighboring filters. These conditions simulated the detrimental effects of suboptimal CI electrode-neuron interfaces on spectral transmission. Vowel and consonant confusion patterns were analyzed with sequential information transmission, perceptual distance, and perceptual vowel space analyses. Results indicated that both types of spectral manipulation were equally destructive. Loss or distortion of frequency information produced similar effects on phoneme identification performance and confusion patterns. Consonant error patterns were consistently based on place of articulation. Vowel confusions showed that perceptions gravitated away from the degraded frequency region in a predictable manner, indicating that vowels can probe frequency-specific regions of spectral degradations.

Highlights

Despite the success of cochlear implants (CIs) in restoring auditory perception, CI users exhibit a wide range of performance on speech perception tasks
Poor interfaces between CI electrodes and auditory neurons, which result from degeneration of adjacent neurons or suboptimal placement of the electrode array, could result in loss or distortion of the spectral information transmitted through those particular channels
Neither the zero nor the split manipulations significantly lowered consonant identification (a 1⁄4 0.002) relative to the control condition for any frequency region, the split manipulation resulted in slightly better identification performance compared to the zero manipulation

Summary

Introduction

Despite the success of cochlear implants (CIs) in restoring auditory perception, CI users exhibit a wide range of performance on speech perception tasks. Poor interfaces between CI electrodes and auditory neurons, which result from degeneration of adjacent neurons or suboptimal placement of the electrode array, could result in loss or distortion of the spectral information transmitted through those particular channels. That spectral distortion may be localized to a specific range of frequencies. The present study implemented a vocoder simulation in normal hearing (NH) listeners to determine the influence of specific regions of frequency distortion on vowel and consonant recognition performance and confusions. Spectral degradations mimicked the negative effects of suboptimal electrode-neuron interfaces on transmission of particular frequencies within a CI. These spectral a)Portions of this work were presented at the Association for Otolaryngology MidWinter Meeting, San Diego, CA, February 2016

Objectives

Methods

Results

Conclusion