How does aging affect recognition of spectrally degraded speech?

A Scoping Review and Meta-Analysis of the Relations Between Cognition and Cochlear Implant Outcomes and the Effect of Quiet Versus Noise Testing Conditions

OBJECTIVES

Evidence continues to emerge of associations between cochlear implant (CI) outcomes and cognitive functions in postlingually deafened adults. While there are multiple factors that appear to affect these associations, the impact of speech recognition background testing conditions (i.e., in quiet versus noise) has not been systematically explored. The two aims of this study were to (1) identify associations between speech recognition following cochlear implantation and performance on cognitive tasks, and to (2) investigate the impact of speech testing in quiet versus noise on these associations. Ultimately, we want to understand the conditions that impact this complex relationship between CI outcomes and cognition.

DESIGN

A scoping review following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines was performed on published literature evaluating the relation between outcomes of cochlear implantation and cognition. The current review evaluates 39 papers that reported associations between over 30 cognitive assessments and speech recognition tests in adult patients with CIs. Six cognitive domains were evaluated: Global Cognition, Inhibition-Concentration, Memory and Learning, Controlled Fluency, Verbal Fluency, and Visuospatial Organization. Meta-analysis was conducted on three cognitive assessments among 12 studies to evaluate relations with speech recognition outcomes. Subgroup analyses were performed to identify whether speech recognition testing in quiet versus in background noise impacted its association with cognitive performance.

RESULTS

Significant associations between cognition and speech recognition in a background of quiet or noise were found in 69% of studies. Tests of Global Cognition and Inhibition-Concentration skills resulted in the highest overall frequency of significant associations with speech recognition (45% and 57%, respectively). Despite the modest proportion of significant associations reported, pooling effect sizes across samples through meta-analysis revealed a moderate positive correlation between tests of Global Cognition (r = +0.37, p < 0.01) as well as Verbal Fluency (r = +0.44, p < 0.01) and postoperative speech recognition skills. Tests of Memory and Learning are most frequently utilized in the setting of CI (in 26 of 39 included studies), yet meta-analysis revealed nonsignificant associations with speech recognition performance in a background of quiet (r = +0.30, p = 0.18), and noise (r = -0.06, p = 0.78).

CONCLUSIONS

Background conditions of speech recognition testing may influence the relation between speech recognition outcomes and cognition. The magnitude of this effect of testing conditions on this relationship appears to vary depending on the cognitive construct being assessed. Overall, Global Cognition and Inhibition-Concentration skills are potentially useful in explaining speech recognition skills following cochlear implantation. Future work should continue to evaluate these relations to appropriately unify cognitive testing opportunities in the setting of cochlear implantation.

Extraordinary Speech and Language Outcomes After Auditory Brainstem Implantation: Guidance From a Case Study

PURPOSE

Large individual differences and poor speech recognition outcomes are routinely observed in most patients who have received auditory brainstem implants (ABIs). A case report of an ABI recipient with exceptionally good speech recognition outcomes presents an opportunity to better understand the core information processing mechanisms that underlie variability and individual differences in outcomes.

METHOD

A case study is reported of an adult ABI recipient (ID-006) with postlingually acquired, Neurofibromatosis Type 2 (NF2)-related hearing loss who displayed exceptional postoperative speech recognition scores. A novel battery of assessment measures was used to evaluate ID-006's auditory, cognitive, and linguistic information processing skills.

RESULTS

Seventeen years following ABI activation, ID-006 scored 77.6% correct on the AzBio Sentences in quiet. On auditory processing tasks, ID-006 scored higher on tasks with meaningful sentences and much lower on tasks that relied exclusively on audibility. ID-006 also demonstrated exceptionally strong abilities on several cognitive and linguistic information processing tasks.

CONCLUSIONS

Results from a novel battery of information processing tests suggest that ID-006 relies extensively on top-down predictive processing and cognitive control strategies to efficiently encode and process auditory information provided by his ABI. Results suggest that current measures of outcomes and benefits should be expanded beyond conventional speech recognition measures to include more sensitive and robust measures of speech recognition as well as neurocognitive measures such as executive function, working memory, and lexical access.

Emerging Relations among Cognitive Constructs and Cochlear Implant Outcomes: A Systematic Review and Meta-Analysis

OBJECTIVE

Hearing loss has a detrimental impact on cognitive function. However, there is a lack of consensus on the impact of cochlear implants on cognition. This review systematically evaluates whether cochlear implants in adult patients lead to cognitive improvements and investigates the relations of cognition with speech recognition outcomes.

DATA SOURCES

A literature review was performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Studies evaluating cognition and cochlear implant outcomes in postlingual, adult patients from January 1996 to December 2021 were included. Of 2510 total references, 52 studies were included in qualitative analysis and 11 in meta-analyses.

REVIEW METHODS

Proportions were extracted from studies of (1) the significant impacts of cochlear implantation on 6 cognitive domains and (2) associations between cognition and speech recognition outcomes. Meta-analyses were performed using random effects models on mean differences between pre- and postoperative performance on 4 cognitive assessments.

RESULTS

Only half of the outcomes reported suggested cochlear implantation had a significant impact on cognition (50.8%), with the highest proportion in assessments of memory & learning and inhibition-concentration. Meta-analyses revealed significant improvements in global cognition and inhibition-concentration. Finally, 40.4% of associations between cognition and speech recognition outcomes were significant.

CONCLUSION

Findings relating to cochlear implantation and cognition vary depending on the cognitive domain assessed and the study goal. Nonetheless, assessments of memory & learning, global cognition, and inhibition-concentration may represent tools to assess cognitive benefit after implantation and help explain variability in speech recognition outcomes. Enhanced selectivity in assessments of cognition is needed for clinical applicability.

Frequency detection, frequency discrimination, and spectro-temporal pattern perception in older and younger typically hearing adults

Elderly adults often experience difficulties in speech understanding, possibly due to age-related deficits in frequency perception. It is unclear whether age-related deficits in frequency perception differ between the apical or basal regions of the cochlea. It is also unclear how aging might differently affect frequency discrimination or detection of a change in frequency within a stimulus. In the present study, pure-tone frequency thresholds were measured in 19 older (61-74 years) and 20 younger (22-28 years) typically hearing adults. Participants were asked to discriminate between reference and probe frequencies or to detect changes in frequency within a probe stimulus. Broadband spectro-temporal pattern perception was also measured using the spectro-temporal modulated ripple test (SMRT). Frequency thresholds were significantly poorer in the basal than in the apical region of the cochlea; the deficit in the basal region was 2 times larger for the older than for the younger group. Frequency thresholds were significantly poorer in the older group, especially in the basal region where frequency detection thresholds were 3.9 times poorer for the older than for the younger group. SMRT thresholds were 1.5 times better for the younger than for the older group. Significant age effects were observed for SMRT thresholds and for frequency thresholds only in the basal region. SMRT thresholds were significantly correlated with frequency thresholds only in the older group. The poorer frequency and spectro-temporal pattern perception may contribute to age-related deficits in speech perception, even when audiometric thresholds are nearly normal.

Neuropsychological Functions and Audiological Findings in Elderly Cochlear Implant Users: The Role of Attention in Postoperative Performance

Objectives: The present study aimed to investigate in a group of elderly CI users working memory and attention, conventionally considered as predictors of better CI performance and to try to disentangle the effects of these cognitive domains on speech perception, finding potential markers of cognitive decline related to audiometric findings. Methods Thirty postlingually deafened CI users aged >60 underwent an audiological evaluation followed by a cognitive assessment of attention and verbal working memory. A correlation analysis was performed to evaluate the associations between cognitive variables while a simple regression investigated the relationships between cognitive and audiological variables. Comparative analysis was performed to compare variables on the basis of subjects’ attention performance. Results: Attention was found to play a significant role in sound field and speech perception. Univariate analysis found a significant difference between poor and high attention performers, while regression analysis showed that attention significantly predicted recognition of words presented at Signal/Noise +10. Further, the high attention performers showed significantly higher scores than low attentional performers for all working memory tasks. Conclusion: Overall findings confirmed that a better cognitive performance may positively contribute to better speech perception outcomes, especially in complex listening situations. WM may play a crucial role in storage and processing of auditory-verbal stimuli and a robust attention may lead to better performance for speech perception in noise. Implementation of cognitive training in auditory rehabilitation of CI users should be investigated in order to improve cognitive and audiological performance in elderly CI users.

Exploring neurocognitive factors and brain activation in adult cochlear implant recipients associated with speech perception outcomes-A scoping review

Background

Cochlear implants (CIs) are considered an effective treatment for severe-to-profound sensorineural hearing loss. However, speech perception outcomes are highly variable among adult CI recipients. Top-down neurocognitive factors have been hypothesized to contribute to this variation that is currently only partly explained by biological and audiological factors. Studies investigating this, use varying methods and observe varying outcomes, and their relevance has yet to be evaluated in a review. Gathering and structuring this evidence in this scoping review provides a clear overview of where this research line currently stands, with the aim of guiding future research.

Objective

To understand to which extent different neurocognitive factors influence speech perception in adult CI users with a postlingual onset of hearing loss, by systematically reviewing the literature.

Methods

A systematic scoping review was performed according to the PRISMA guidelines. Studies investigating the influence of one or more neurocognitive factors on speech perception post-implantation were included. Word and sentence perception in quiet and noise were included as speech perception outcome metrics and six key neurocognitive domains, as defined by the DSM-5, were covered during the literature search (Protocol in open science registries: 10.17605/OSF.IO/Z3G7W of searches in June 2020, April 2022).

Results

From 5,668 retrieved articles, 54 articles were included and grouped into three categories using different measures to relate to speech perception outcomes: (1) Nineteen studies investigating brain activation, (2) Thirty-one investigating performance on cognitive tests, and (3) Eighteen investigating linguistic skills.

Conclusion

The use of cognitive functions, recruiting the frontal cortex, the use of visual cues, recruiting the occipital cortex, and the temporal cortex still available for language processing, are beneficial for adult CI users. Cognitive assessments indicate that performance on non-verbal intelligence tasks positively correlated with speech perception outcomes. Performance on auditory or visual working memory, learning, memory and vocabulary tasks were unrelated to speech perception outcomes and performance on the Stroop task not to word perception in quiet. However, there are still many uncertainties regarding the explanation of inconsistent results between papers and more comprehensive studies are needed e.g., including different assessment times, or combining neuroimaging and behavioral measures.

Systematic review registration

https://doi.org/10.17605/OSF.IO/Z3G7W.

Noise-Vocoded Sentence Recognition and the Use of Context in Older and Younger Adult Listeners

PURPOSE

When listening to speech under adverse conditions, older adults, even with "age-normal" hearing, face challenges that may lead to poorer speech recognition than their younger peers. Older listeners generally demonstrate poorer suprathreshold auditory processing along with aging-related declines in neurocognitive functioning that may impair their ability to compensate using "top-down" cognitive-linguistic functions. This study explored top-down processing in older and younger adult listeners, specifically the use of semantic context during noise-vocoded sentence recognition.

METHOD

Eighty-four adults with age-normal hearing (45 young normal-hearing [YNH] and 39 older normal-hearing [ONH] adults) participated. Participants were tested for recognition accuracy for two sets of noise-vocoded sentence materials: one that was semantically meaningful and the other that was syntactically appropriate but semantically anomalous. Participants were also tested for hearing ability and for neurocognitive functioning to assess working memory capacity, speed of lexical access, inhibitory control, and nonverbal fluid reasoning, as well as vocabulary knowledge.

RESULTS

The ONH and YNH listeners made use of semantic context to a similar extent. Nonverbal reasoning predicted recognition of both meaningful and anomalous sentences, whereas pure-tone average contributed additionally to anomalous sentence recognition. None of the hearing, neurocognitive, or language measures significantly predicted the amount of context gain, computed as the difference score between meaningful and anomalous sentence recognition. However, exploratory cluster analyses demonstrated four listener profiles and suggested that individuals may vary in the strategies used to recognize speech under adverse listening conditions.

CONCLUSIONS

Older and younger listeners made use of sentence context to similar degrees. Nonverbal reasoning was found to be a contributor to noise-vocoded sentence recognition. However, different listeners may approach the problem of recognizing meaningful speech under adverse conditions using different strategies based on their hearing, neurocognitive, and language profiles. These findings provide support for the complexity of bottom-up and top-down interactions during speech recognition under adverse listening conditions.

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.

Lexical Effects on the Perceived Clarity of Noise-Vocoded Speech in Younger and Older Listeners

When listening to degraded speech, such as speech delivered by a cochlear implant (CI), listeners make use of top-down linguistic knowledge to facilitate speech recognition. Lexical knowledge supports speech recognition and enhances the perceived clarity of speech. Yet, the extent to which lexical knowledge can be used to effectively compensate for degraded input may depend on the degree of degradation and the listener's age. The current study investigated lexical effects in the compensation for speech that was degraded via noise-vocoding in younger and older listeners. In an online experiment, younger and older normal-hearing (NH) listeners rated the clarity of noise-vocoded sentences on a scale from 1 ("very unclear") to 7 ("completely clear"). Lexical information was provided by matching text primes and the lexical content of the target utterance. Half of the sentences were preceded by a matching text prime, while half were preceded by a non-matching prime. Each sentence also consisted of three key words of high or low lexical frequency and neighborhood density. Sentences were processed to simulate CI hearing, using an eight-channel noise vocoder with varying filter slopes. Results showed that lexical information impacted the perceived clarity of noise-vocoded speech. Noise-vocoded speech was perceived as clearer when preceded by a matching prime, and when sentences included key words with high lexical frequency and low neighborhood density. However, the strength of the lexical effects depended on the level of degradation. Matching text primes had a greater impact for speech with poorer spectral resolution, but lexical content had a smaller impact for speech with poorer spectral resolution. Finally, lexical information appeared to benefit both younger and older listeners. Findings demonstrate that lexical knowledge can be employed by younger and older listeners in cognitive compensation during the processing of noise-vocoded speech. However, lexical content may not be as reliable when the signal is highly degraded. Clinical implications are that for adult CI users, lexical knowledge might be used to compensate for the degraded speech signal, regardless of age, but some CI users may be hindered by a relatively poor signal.

Bottom-Up Signal Quality Impacts the Role of Top-Down Cognitive-Linguistic Processing During Speech Recognition by Adults with Cochlear Implants

HYPOTHESES

Significant variability persists in speech recognition outcomes in adults with cochlear implants (CIs). Sensory ("bottom-up") and cognitive-linguistic ("top-down") processes help explain this variability. However, the interactions of these bottom-up and top-down factors remain unclear. One hypothesis was tested: top-down processes would contribute differentially to speech recognition, depending on the fidelity of bottom-up input.

BACKGROUND

Bottom-up spectro-temporal processing, assessed using a Spectral-Temporally Modulated Ripple Test (SMRT), is associated with CI speech recognition outcomes. Similarly, top-down cognitive-linguistic skills relate to outcomes, including working memory capacity, inhibition-concentration, speed of lexical access, and nonverbal reasoning.

METHODS

Fifty-one adult CI users were tested for word and sentence recognition, along with performance on the SMRT and a battery of cognitive-linguistic tests. The group was divided into "low-," "intermediate-," and "high-SMRT" groups, based on SMRT scores. Separate correlation analyses were performed for each subgroup between a composite score of cognitive-linguistic processing and speech recognition.

RESULTS

Associations of top-down composite scores with speech recognition were not significant for the low-SMRT group. In contrast, these associations were significant and of medium effect size (Spearman's rho = 0.44-0.46) for two sentence types for the intermediate-SMRT group. For the high-SMRT group, top-down scores were associated with both word and sentence recognition, with medium to large effect sizes (Spearman's rho = 0.45-0.58).

CONCLUSIONS

Top-down processes contribute differentially to speech recognition in CI users based on the quality of bottom-up input. Findings have clinical implications for individualized treatment approaches relying on bottom-up device programming or top-down rehabilitation approaches.

Talker Adaptation and Lexical Difficulty Impact Word Recognition in Adults with Cochlear Implants

INTRODUCTION

Talker-specific adaptation facilitates speech recognition in normal-hearing listeners. This study examined talker adaptation in adult cochlear implant (CI) users. Three hypotheses were tested: (1) high-performing adult CI users show improved word recognition following exposure to a talker ("talker adaptation"), particularly for lexically hard words, (2) individual performance is determined by auditory sensitivity and neurocognitive skills, and (3) individual performance relates to real-world functioning.

METHODS

Fifteen high-performing, post-lingually deaf adult CI users completed a word recognition task consisting of 6 single-talker blocks (3 female/3 male native English speakers); words were lexically "easy" and "hard." Recognition accuracy was assessed "early" and "late" (first vs. last 10 trials); adaptation was assessed as the difference between late and early accuracy. Participants also completed measures of spectral-temporal processing and neurocognitive skills, as well as real-world measures of multiple-talker sentence recognition and quality of life (QoL).

RESULTS

CI users showed limited talker adaptation overall, but performance improved for lexically hard words. Stronger spectral-temporal processing and neurocognitive skills were weakly to moderately associated with more accurate word recognition and greater talker adaptation for hard words. Finally, word recognition accuracy for hard words was moderately related to multiple-talker sentence recognition and QoL.

CONCLUSION

Findings demonstrate a limited talker adaptation benefit for recognition of hard words in adult CI users. Both auditory sensitivity and neurocognitive skills contribute to performance, suggesting additional benefit from adaptation for individuals with stronger skills. Finally, processing differences related to talker adaptation and lexical difficulty may be relevant to real-world functioning.

Forward Digit Span and Word Familiarity Do Not Correlate With Differences in Speech Recognition in Individuals With Cochlear Implants After Accounting for Auditory Resolution

Purpose In individuals with cochlear implants, speech recognition is not associated with tests of working memory that primarily reflect storage, such as forward digit span. In contrast, our previous work found that vocoded speech recognition in individuals with normal hearing was correlated with performance on a forward digit span task. A possible explanation for this difference across groups is that variability in auditory resolution across individuals with cochlear implants could conceal the true relationship between speech and memory tasks. Here, our goal was to determine if performance on forward digit span and speech recognition tasks are correlated in individuals with cochlear implants after controlling for individual differences in auditory resolution. Method We measured sentence recognition ability in 20 individuals with cochlear implants with Perceptually Robust English Sentence Test Open-set sentences. Spectral and temporal modulation detection tasks were used to assess individual differences in auditory resolution, auditory forward digit span was used to assess working memory storage, and self-reported word familiarity was used to assess vocabulary. Results Individual differences in speech recognition were predicted by spectral and temporal resolution. A correlation was found between forward digit span and speech recognition, but this correlation was not significant after controlling for spectral and temporal resolution. No relationship was found between word familiarity and speech recognition. Forward digit span performance was not associated with individual differences in auditory resolution. Conclusions Our findings support the idea that sentence recognition in individuals with cochlear implants is primarily limited by individual differences in working memory processing, not storage. Studies examining the relationship between speech and memory should control for individual differences in auditory resolution.

Speech Recognition as a Function of Age and Listening Experience in Adult Cochlear Implant Users

OBJECTIVES/HYPOTHESIS

Speech recognition with a cochlear implant (CI) tends to be better for younger adults than older adults. However, older adults may take longer to reach asymptotic performance than younger adults. The present study aimed to characterize speech recognition as a function of age at implantation and listening experience for adult CI users.

STUDY DESIGN

Retrospective review.

METHODS

A retrospective review identified 352 adult CI recipients (387 ears) with at least 5 years of device listening experience. Speech recognition, as measured with consonant-nucleus-consonant (CNC) words in quiet and AzBio sentences in a 10-talker noise masker (10 dB signal-to-noise ratio), was reviewed at 1, 5, and 10 years postactivation.

RESULTS

Speech recognition was better in younger listeners, and performance was stable or continued to improve through 10 years of CI listening experience. There was no indication of differences in acclimatization as a function of age at implantation. For the better performing CI recipients, an effect of age at implantation was more apparent for sentence recognition in noise than for word recognition in quiet.

CONCLUSIONS

Adult CI recipients across the age range examined here experience speech recognition benefit with a CI. However, older adults perform more poorly than young adults for speech recognition in quiet and noise, with similar age effects through 5 to 10 years of listening experience.

LEVEL OF EVIDENCE

3 Laryngoscope, 131:2106-2111, 2021.

A Longitudinal Comparison of Environmental Sound Recognition in Adults With Hearing Aids Before and After Cochlear Implantation

Purpose The aims of this study were (a) to longitudinally assess environmental sound recognition (ESR) before and after cochlear implantation in a sample of postlingually deafened adults and (b) to assess the extent to which spectro-temporal processing abilities influence ESR with cochlear implants (CIs). Method In a longitudinal cohort study, 20 postlingually deafened adults were tested with hearing aids on the Familiar Environmental Sound Test-Identification and AzBio sentences in quiet pre-CI and 6 months post-CI. A subset of 11 participants were also tested 12 months post-CI. Pre-CI spectro-temporal processing was assessed using the Spectral-temporally Modulated Ripple Test. Results Average ESR accuracy pre-CI (M = 63.60%) was not significantly different from ESR accuracy at 6 months (M = 65.40%) or 12 months (M = 69.09%) post-CI. In 11 participants (55%), however, ESR improved following implantation by 10.91 percentage points, on average. Pre-CI ESR correlated moderately and significantly with pre-CI and 12-month post-CI AzBio scores, with a trend toward significance for AzBio performance at 6 months. Pre-CI spectro-temporal processing was moderately associated with ESR at 6 and 12 months post-CI but not with speech recognition post-CI. Conclusions The present findings failed to demonstrate an overall significant improvement in ESR following implantation. Nevertheless, more than half of our sample showed some degree of improvement in ESR. Several environmental sounds were poorly identified both before and after implantation. Spectro-temporal processing ability prior to implantation appears to predict postimplantation performance for ESR. These findings indicate the need for greater attention to ESR following cochlear implantation and for developing individualized targets for ESR rehabilitation. Supplemental Material https://doi.org/10.23641/asha.13876745.

A surgeon-scientist's perspective and review of cognitive-linguistic contributions to adult cochlear implant outcomes

OBJECTIVES

Enormous variability in speech recognition outcomes persists in adults who receive cochlear implants (CIs), which leads to a barrier to progress in predicting outcomes before surgery, explaining "poor" outcomes, and determining how to provide tailored rehabilitation therapy for individual CI users. The primary goal of my research program over the past 9 years has been to extend our understanding of the contributions of "top-down" cognitive-linguistic skills to CI outcomes in adults, acknowledging that "bottom-up" sensory processes also contribute substantially. The main objective of this invited narrative review is to provide an overview of this work. A secondary objective is to provide career "guidance points" to budding surgeon-scientists in Otolaryngology.

METHODS

A narrative, chronological review covers work done by our group to explore top-down and bottom-up processing in adult CI outcomes. A set of ten guidance points is also provided to assist junior Otolaryngology surgeon-scientists.

RESULTS

Work in our lab has identified substantial contributions of cognitive skills (working memory, inhibition-concentration, speed of lexical access, nonverbal reasoning, verbal learning and memory) as well as linguistic abilities (acoustic cue-weighting, phonological sensitivity) to speech recognition outcomes in adults with CIs. These top-down skills interact with the quality of the bottom-up input.

CONCLUSION

Although progress has been made in understanding speech recognition variability in adult CI users, future work is needed to predict CI outcomes before surgery, to identify particular patients' strengths and weaknesses, and to tailor rehabilitation approaches for individual CI users.

LEVEL OF EVIDENCE

4.

Comprehensive auditory rehabilitation in adults receiving cochlear implants: A pilot study

OBJECTIVE

In the United States, most adults who receive cochlear implants (CIs) do not undergo a comprehensive auditory rehabilitation (CAR) approach, which may result in suboptimal outcomes. The objectives of this pilot study were to demonstrate that a CAR approach incorporating auditory training (AT) by a speech-language pathologist (SLP) is feasible in adults receiving CIs and to explore whether this approach results in improved outcomes.

METHODS

Twenty-four postlingually deaf adult CI candidates were serially assigned to one of three groups: (a) a "CAR group" that received standard of care implantation, programming by an audiologist, an additional preoperative counseling session, and eight one-hour AT sessions; (b) a "passive control" standard-of-care group; and (c) an "active control" group that also received the extra preoperative counseling session. Participants were tested preoperatively and 1, 3, and 6 months after CI using measures of word and sentence recognition in quiet and in babble, as well as measures of quality of life (QOL).

RESULTS

The CAR approach was feasible, but this pilot study was underpowered to determine efficacy. Differential time courses of speech recognition improvement were seen for sentence and word recognition. All QOL measurements showed improvement from pre-CI to 1 month post-CI activation. Results revealed issues to consider for a larger-scale study of CAR revolving around participant selection, study measures, and sample size.

CONCLUSION

The CAR approach is feasible in new CI users. A larger trial is needed to investigate whether CAR leads to better outcomes or faster improvement in this clinical population.

LEVEL OF EVIDENCE

2.

Explaining Speech Recognition and Quality of Life Outcomes in Adult Cochlear Implant Users: Complementary Contributions of Demographic, Sensory, and Cognitive Factors

HYPOTHESES

Adult cochlear implant (CI) outcomes depend on demographic, sensory, and cognitive factors. However, these factors have not been examined together comprehensively for relations to different outcome types, such as speech recognition versus quality of life (QOL). Three hypotheses were tested: 1) speech recognition will be explained most strongly by sensory factors, whereas QOL will be explained more strongly by cognitive factors. 2) Different speech recognition outcome domains (sentences versus words) and different QOL domains (physical versus social versus psychological functioning) will be explained differentially by demographic, sensory, and cognitive factors. 3) Including cognitive factors as predictors will provide more power to explain outcomes than demographic and sensory predictors alone.

BACKGROUND

A better understanding of the contributors to CI outcomes is needed to prognosticate outcomes before surgery, explain outcomes after surgery, and tailor rehabilitation efforts.

METHODS

Forty-one adult postlingual experienced CI users were assessed for sentence and word recognition, as well as hearing-related QOL, along with a broad collection of predictors. Partial least squares regression was used to identify factors that were most predictive of outcome measures.

RESULTS

Supporting our hypotheses, speech recognition abilities were most strongly dependent on sensory skills, while QOL outcomes required a combination of cognitive, sensory, and demographic predictors. The inclusion of cognitive measures increased the ability to explain outcomes, mainly for QOL.

CONCLUSIONS

Explaining variability in adult CI outcomes requires a broad assessment approach. Identifying the most important predictors depends on the particular outcome domain and even the particular measure of interest.

Psychoacoustic and Demographic Factors for Speech Recognition of Older Adult Cochlear Implant Users

Purpose This study aimed to evaluate the effects of aging and cochlear implant (CI) on psychoacoustic and speech recognition abilities and to assess the relative contributions of psychoacoustic and demographic factors to speech recognition of older CI (OCI) users. Method Twelve OCI users, 12 older acoustic-hearing (OAH) listeners age-matched to OCI users, and 12 younger normal-hearing (YNH) listeners underwent tests of temporal amplitude modulation detection, temporal gap detection in noise, and spectral-temporal modulated ripple discrimination. Speech reception thresholds were measured for sentence recognition in multitalker, speech-babble noise. Results Statistical analyses showed that, for the small sample of OAH listeners, the degree of hearing loss did not significantly affect any outcome measure. Temporal resolution, spectral resolution, and speech recognition all significantly degraded with both age and the use of a CI (i.e., YNH better than OAH and OAH better than OCI performance). Although both were significantly correlated with OCI users' speech recognition, the duration of CI use no longer had a significant effect on speech recognition once the effect of spectral-temporal ripple discrimination performance was taken into account. For OAH listeners, the only significant predictor of speech recognition was temporal gap detection performance. Conclusion The preliminary results suggest that speech recognition of OCI users may improve with longer duration of CI use, mainly due to higher perceptual acuity to spectral-temporal modulated ripples in acoustic stimuli.

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.

Influence of Age at Cochlear Implantation and Frequency-to-Place Mismatch on Early Speech Recognition in Adults

OBJECTIVE

Default frequency filters of cochlear implant (CI) devices assign frequency information irrespective of intracochlear position, resulting in varying degrees of frequency-to-place mismatch. Substantial mismatch negatively influences speech recognition in postlingually deafened CI recipients, and acclimatization may be particularly challenging for older adults due to effects of aging on the auditory pathway. The present report investigated the influence of mismatch and age at implantation on speech recognition within the initial 6 months of CI use.

STUDY DESIGN

Retrospective review.

SETTING

Tertiary referral center.

SUBJECTS AND METHODS

Forty-eight postlingually deafened adult CI recipients of lateral wall electrode arrays underwent postoperative computed tomography to determine angular insertion depth of each electrode contact. Frequency-to-place mismatch was determined by comparing spiral ganglion place frequencies to default frequency filters. Consonant-nucleus-consonant (CNC) scores in the CI-alone condition at 1, 3, and 6 months postactivation were compared to the degree of mismatch at 1500 Hz and age at implantation.

RESULTS

Younger adult CI recipients experienced more rapid growth in speech recognition during the initial 6 months postactivation. Greater degrees of frequency-to-place mismatch were associated with poorer performance, yet older listeners were not particularly susceptible to this effect.

CONCLUSIONS

While older adults are not necessarily more sensitive to detrimental effects of frequency-to-place mismatch, other factors appear to limit early benefit with a CI in this population. These results suggest that minimizing mismatch could optimize outcomes in adult CI recipients across the life span, which may be particularly beneficial in the elderly considering auditory processing deficits associated with advanced age.

How Does Nonverbal Reasoning Affect Sentence Recognition in Adults with Cochlear Implants and Normal-Hearing Peers?

BACKGROUND

Previous research has demonstrated an association of scores on a visual test of nonverbal reasoning, Raven's Progressive Matrices (RPM), with scores on open-set sentence recognition in quiet for adult cochlear implant (CI) users as well as for adults with normal hearing (NH) listening to noise-vocoded sentence materials. Moreover, in that study, CI users demonstrated poorer nonverbal reasoning when compared with NH peers. However, it remains unclear what underlying neurocognitive processes contributed to the association of nonverbal reasoning scores with sentence recognition, and to the poorer scores demonstrated by CI users.

OBJECTIVES

Three hypotheses were tested: (1) nonverbal reasoning abilities of adult CI users and normal-hearing (NH) age-matched peers would be predicted by performance on more basic neurocognitive measures of working memory capacity, information-processing speed, inhibitory control, and concentration; (2) nonverbal reasoning would mediate the effects of more basic neurocognitive functions on sentence recognition in both groups; and (3) group differences in more basic neurocognitive functions would explain the group differences previously demonstrated in nonverbal reasoning.

METHOD

Eighty-three participants (40 CI and 43 NH) underwent testing of sentence recognition using two sets of sentence materials: sentences produced by a single male talker (Harvard sentences) and high-variability sentences produced by multiple talkers (Perceptually Robust English Sentence Test Open-set, PRESTO). Participants also completed testing of nonverbal reasoning using a visual computerized RPM test, and additional neurocognitive assessments were collected using a visual Digit Span test and a Stroop Color-Word task. Multivariate regression analyses were performed to test our hypotheses while treating age as a covariate.

RESULTS

In the CI group, information processing speed on the Stroop task predicted RPM performance, and RPM scores mediated the effects of information processing speed on sentence recognition abilities for both Harvard and PRESTO sentences. In contrast, for the NH group, Stroop inhibitory control predicted RPM performance, and a trend was seen towards RPM scores mediating the effects of inhibitory control on sentence recognition, but only for PRESTO sentences. Poorer RPM performance in CI users than NH controls could be partially attributed to slower information processing speed.

CONCLUSIONS

Neurocognitive functions contributed differentially to nonverbal reasoning performance in CI users as compared with NH peers, and nonverbal reasoning appeared to partially mediate the effects of these different neurocognitive functions on sentence recognition in both groups, at least for PRESTO sentences. Slower information processing speed accounted for poorer nonverbal reasoning scores in CI users. Thus, it may be that prolonged auditory deprivation contributes to cognitive decline through slower information processing.