Perceptual Discrimination of Speaking Style Under Cochlear Implant Simulation

Evaluating Listening Effort in Unilateral, Bimodal, and Bilateral Cochlear Implant Users

OBJECTIVE

Evaluate listening effort (LE) in unilateral, bilateral, and bimodal cochlear implant (CI) users. Establish an easy-to-implement task of LE that could be useful for clinical decision making.

STUDY DESIGN

Prospective cohort study.

SETTING

Tertiary neurotology center.

METHODS

The Sentence Final Word Identification and Recall Task, an established measure of LE, was modified to include challenging listening conditions (multitalker babble, gender, and emotional variation; test), in addition to single-talker sentences (control). Participants listened to lists of sentences in each condition and recalled the last word of each sentence. LE was quantified by percentage of words correctly recalled and was compared across conditions, across CI groups, and within subjects (best aided vs monaural).

RESULTS

A total of 24 adults between the ages of 37 and 82 years enrolled, including 4 unilateral CI users (CI), 10 bilateral CI users (CICI), and 10 bimodal CI users (CIHA). Task condition impacted LE (P < .001), but hearing configuration and listener group did not (P = .90). Working memory capacity and contralateral hearing contributed to individual performance.

CONCLUSION

This study adds to the growing body of literature on LE in challenging listening conditions for CI users and demonstrates feasibility of a simple behavioral task that could be implemented clinically to assess LE. This study also highlights the potential benefits of bimodal hearing and individual hearing and cognitive factors in understanding individual differences in performance, which will be evaluated through further research.

The relation between speaking-style categorization and speech recognition in adult cochlear implant users

The current study examined the relation between speaking-style categorization and speech recognition in post-lingually deafened adult cochlear implant users and normal-hearing listeners tested under 4- and 8-channel acoustic noise-vocoder cochlear implant simulations. Across all listeners, better speaking-style categorization of careful read and casual conversation speech was associated with more accurate recognition of speech across those same two speaking styles. Findings suggest that some cochlear implant users and normal-hearing listeners under cochlear implant simulation may benefit from stronger encoding of indexical information in speech, enabling both better categorization and recognition of speech produced in different speaking styles.

Factors affecting talker discrimination ability in adult cochlear implant users

INTRODUCTION

Real-world speech communication involves interacting with many talkers with diverse voices and accents. Many adults with cochlear implants (CIs) demonstrate poor talker discrimination, which may contribute to real-world communication difficulties. However, the factors contributing to talker discrimination ability, and how discrimination ability relates to speech recognition outcomes in adult CI users are still unknown. The current study investigated talker discrimination ability in adult CI users, and the contributions of age, auditory sensitivity, and neurocognitive skills. In addition, the relation between talker discrimination ability and multiple-talker sentence recognition was explored.

METHODS

Fourteen post-lingually deaf adult CI users (3 female, 11 male) with ≥1 year of CI use completed a talker discrimination task. Participants listened to two monosyllabic English words, produced by the same talker or by two different talkers, and indicated if the words were produced by the same or different talkers. Nine female and nine male native English talkers were paired, resulting in same- and different-talker pairs as well as same-gender and mixed-gender pairs. Participants also completed measures of spectro-temporal processing, neurocognitive skills, and multiple-talker sentence recognition.

RESULTS

CI users showed poor same-gender talker discrimination, but relatively good mixed-gender talker discrimination. Older age and weaker neurocognitive skills, in particular inhibitory control, were associated with less accurate mixed-gender talker discrimination. Same-gender discrimination was significantly related to multiple-talker sentence recognition accuracy.

CONCLUSION

Adult CI users demonstrate overall poor talker discrimination ability. Individual differences in mixed-gender discrimination ability were related to age and neurocognitive skills, suggesting that these factors contribute to the ability to make use of available, degraded talker characteristics. Same-gender talker discrimination was associated with multiple-talker sentence recognition, suggesting that access to subtle talker-specific cues may be important for speech recognition in challenging listening conditions.

Estimating the reduced benefit of infant-directed speech in cochlear implant-related speech processing

Caregivers modify their speech when talking to infants, a specific type of speech known as infant-directed speech (IDS). This speaking style facilitates language learning compared to adult-directed speech (ADS) in infants with normal hearing (NH). While infants with NH and those with cochlear implants (CIs) prefer listening to IDS over ADS, it is yet unknown how CI processing may affect the acoustic distinctiveness between ADS and IDS, as well as the degree of intelligibility of these. This study analyzed speech of seven female adult talkers to model the effects of simulated CI processing on (1) acoustic distinctiveness between ADS and IDS, (2) estimates of intelligibility of caregivers' speech in ADS and IDS, and (3) individual differences in caregivers' ADS-to-IDS modification and estimated speech intelligibility. Results suggest that CI processing is substantially detrimental to the acoustic distinctiveness between ADS and IDS, as well as to the intelligibility benefit derived from ADS-to-IDS modifications. Moreover, the observed variability across individual talkers in acoustic implementation of ADS-to-IDS modification and the estimated speech intelligibility was significantly reduced due to CI processing. The findings are discussed in the context of the link between IDS and language learning in infants with CIs.

High- and Low-Performing Adult Cochlear Implant Users on High-Variability Sentence Recognition: Differences in Auditory Spectral Resolution and Neurocognitive Functioning

BACKGROUND

Postlingually deafened adult cochlear implant (CI) users routinely display large individual differences in the ability to recognize and understand speech, especially in adverse listening conditions. Although individual differences have been linked to several sensory (''bottom-up'') and cognitive (''top-down'') factors, little is currently known about the relative contributions of these factors in high- and low-performing CI users.

PURPOSE

The aim of the study was to investigate differences in sensory functioning and neurocognitive functioning between high- and low-performing CI users on the Perceptually Robust English Sentence Test Open-set (PRESTO), a high-variability sentence recognition test containing sentence materials produced by multiple male and female talkers with diverse regional accents.

RESEARCH DESIGN

CI users with accuracy scores in the upper (HiPRESTO) or lower quartiles (LoPRESTO) on PRESTO in quiet completed a battery of behavioral tasks designed to assess spectral resolution and neurocognitive functioning.

STUDY SAMPLE

Twenty-one postlingually deafened adult CI users, with 11 HiPRESTO and 10 LoPRESTO participants.

DATA COLLECTION AND ANALYSIS

A discriminant analysis was carried out to determine the extent to which measures of spectral resolution and neurocognitive functioning discriminate HiPRESTO and LoPRESTO CI users. Auditory spectral resolution was measured using the Spectral-Temporally Modulated Ripple Test (SMRT). Neurocognitive functioning was assessed with visual measures of working memory (digit span), inhibitory control (Stroop), speed of lexical/phonological access (Test of Word Reading Efficiency), and nonverbal reasoning (Raven's Progressive Matrices).

RESULTS

HiPRESTO and LoPRESTO CI users were discriminated primarily by performance on the SMRT and secondarily by the Raven's test. No other neurocognitive measures contributed substantially to the discriminant function.

CONCLUSIONS

High- and low-performing CI users differed by spectral resolution and, to a lesser extent, nonverbal reasoning. These findings suggest that the extreme groups are determined by global factors of richness of sensory information and domain-general, nonverbal intelligence, rather than specific neurocognitive processing operations related to speech perception and spoken word recognition. Thus, although both bottom-up and top-down information contribute to speech recognition performance, low-performing CI users may not be sufficiently able to rely on neurocognitive skills specific to speech recognition to enhance processing of spectrally degraded input in adverse conditions involving high talker variability.

The impact of speaking style on speech recognition in quiet and multi-talker babble in adult cochlear implant users

The current study examined sentence recognition across speaking styles (conversational, neutral, and clear) in quiet and multi-talker babble (MTB) for cochlear implant (CI) users and normal-hearing listeners under CI simulations. Listeners demonstrated poorer recognition accuracy in MTB than in quiet, but were relatively more accurate with clear speech overall. Within CI users, higher-performing participants were also more accurate in MTB when listening to clear speech. Lower performing users' accuracy was not impacted by speaking style. Clear speech may facilitate recognition in MTB for high-performing users, who may be better able to take advantage of clear speech cues.