Discrimination and Sensorimotor Adaptation of Self-Produced Vowels in Cochlear Implant Users

Abstract

Humans rely on auditory feedback to monitor and adjust their speech for clarity. Cochlear implants (CIs) have helped over a million people restore access to auditory feedback. Access to these feedback signals significantly improves speech production, but there is substantial variability in outcomes. This study aims to investigate the extent to which CI users can use their auditory feedback to detect self-produced sensory errors and make adjustments to their speech, given the coarse spectral resolution provided by their implants. First, we used an auditory discrimination task to assess the sensitivity of CI users to small differences in the formant frequencies of their own self-produced vowels. Then, CI users produced words under conditions of altered auditory feedback in order to assess sensorimotor adaptation to auditory error. Almost half of the CI participants tested can detect small, within-channel differences in their self-produced vowels, and they can also utilize this auditory feedback towards speech adaption. A typical hearing control group showed better sensitivity to the shifts in vowels, even in vocoded speech (CI-simulated speech), and elicited more robust speech adaptation behavior than the CI participants. Nevertheless, this study confirms that CI users can compensate for sensory errors in their speech, and supports the idea that sensitivity to these errors is related to variability in production.