Real‐time feedback control of voice in cochlear implant recipients

Abstract

Objectives: To evaluate feedback-dependent vocal control in cochlear implant patients using pitch-shifted auditory feedback. Methods: Twenty-three CI recipients with at least 6 months of implant experience were enrolled. Vocal recordings were performed while subjects repeated the vowel /e/ and vocal signals were altered in real-time using a digital effects processor to introduce a pitch-shift, presented back to subjects using headphones. Recordings were analyzed to determine pitch changes following the pitch-shifted feedback, and results compared to the magnitude of the shift as well as patient demographics. Results: Consistent with previous results, CI patients' voices had higher pitches with their implant turned off, a change explainable by increases in vocal loudness without the CI. CI patients rapidly compensated for pitch-shifted feedback by changing their vocal pitch, but only for larger shifts. Considerable inter-subject variability was present, and weakly correlated with the duration of implant experience and implant sound thresholds. Conclusions: CI patients, like normal hearing individuals, are capable of real-time feedback-dependent control of their vocal pitch. However, CI patients are less sensitive to small feedback changes, possibly a result of courser CI frequency precision, and may explain poorer than normal vocal control in these patients.

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

“…This wide individual variability in speech adaptation behavior is not uncommon and has been reported by many other studies (Parrell and Niziolek, 2021;Martin et al, 2018;Munhall et al, 2009;Parrell et al, 2017;Villacorta et al, 2007). This variability was also reported in CI participants in f 0 control (Gautam et al, 2020). At the individual level, some CI participants showed even more speech adaptation behavior than some TH participants.…”

“…The phoneme contrast in CI users' speech also improves over time with longer exposure to auditory feedback: significant improvement after just one month post-implantation, and more after one year post-implantation as compared to the pre-implantation status (Ménard et al, 2007). Additionally, similar to TH individuals, CI users also rely on auditory feedback in ongoing speech, producing more errors and speaking at a slower speech rate under conditions of a feedback delay (Taitelbaum-Swead et al, 2019), and changing the pitch of their voice in response to a shift in the fundamental frequency of their auditory feedback (Loucks et al, 2015;Gautam et al, 2020).…”

“…Although past research shows that CI users are capable of perceiving perturbations to their fundamental frequency, there is conflicting evidence as to how sensitive they are to small changes. Gfeller et al (2007) reported that some CI users have the same sensitivity as TH individuals, while other research suggests that CI users are much less sensitive (Gautam et al, 2020). Further, no study with CI users has yet investigated perturbations to formant frequencies, the broad peaks in the spectrum shaped by filtering from the vocal tract, which provide the primary perceptual cues to vowels and some consonants.…”

Effects of Cortical Stimulation on Feedback‐Dependent Vocal Control in Non‐Human Primates

“…8 Recent results have suggested that implant recipients, for example, do have some ability to monitor and their auditory feedback, but that these abilities lack the fine control seen in normal individuals. 9 Additionally, dysfunction of vocal selfmonitoring and resulting feedback-dependent vocal control has also been seen in a variety of primary vocal disorders and neurologic disorders with vocal symptoms, including spasmodic dysphonia, 10 vocal cord paralysis, 11 Parkinson's disease, 12 and cerebellar degeneration. 13 A better understanding of the underlying neural and behavioral mechanisms may lead to better diagnostic and rehabilitation tools to improve patient communication deficits.…”

“…Unfortunately, although hearing restoration, including cochlear implants, improves vocal control and clarity of speech production, the communication abilities of these patients still lag behind those of normal hearing individuals 8 . Recent results have suggested that implant recipients, for example, do have some ability to monitor and their auditory feedback, but that these abilities lack the fine control seen in normal individuals 9 . Additionally, dysfunction of vocal self‐monitoring and resulting feedback‐dependent vocal control has also been seen in a variety of primary vocal disorders and neurologic disorders with vocal symptoms, including spasmodic dysphonia, 10 vocal cord paralysis, 11 Parkinson's disease, 12 and cerebellar degeneration 13 .…”