Learning, Memory, and Cognitive Processes in Deaf Children Following Cochlear Implantation. In: Zeng F, Popper AN, Fay RR, editors. Cochlear Implants: Auditory Prostheses and Electric Hearing. New York: Springer; 2004. pp. 377-426. [DOI: 10.1007/978-0-387-22585-2_9]

Auditory but Not Audiovisual Cues Lead to Higher Neural Sensitivity to the Statistical Regularities of an Unfamiliar Musical Style

It is still a matter of debate whether visual aids improve learning of music. In a multisession study, we investigated the neural signatures of novel music sequence learning with or without aids (auditory-only: AO, audiovisual: AV). During three training sessions on three separate days, participants (nonmusicians) reproduced (note by note on a keyboard) melodic sequences generated by an artificial musical grammar. The AV group (n = 20) had each note color-coded on screen, whereas the AO group (n = 20) had no color indication. We evaluated learning of the statistical regularities of the novel music grammar before and after training by presenting melodies ending on correct or incorrect notes and by asking participants to judge the correctness and surprisal of the final note, while EEG was recorded. We found that participants successfully learned the new grammar. Although the AV group, as compared to the AO group, reproduced longer sequences during training, there was no significant difference in learning between groups. At the neural level, after training, the AO group showed a larger N100 response to low-probability compared with high-probability notes, suggesting an increased neural sensitivity to statistical properties of the grammar; this effect was not observed in the AV group. Our findings indicate that visual aids might improve sequence reproduction while not necessarily promoting better learning, indicating a potential dissociation between sequence reproduction and learning. We suggest that the difficulty induced by auditory-only input during music training might enhance cognitive engagement, thereby improving neural sensitivity to the underlying statistical properties of the learned material.

"Product" Versus "Process" Measures in Assessing Speech Recognition Outcomes in Adults With Cochlear Implants

HYPOTHESES

1) When controlling for age in postlingual adult cochlear implant (CI) users, information-processing functions, as assessed using "process" measures of working memory capacity, inhibitory control, information-processing speed, and fluid reasoning, will predict traditional "product" outcome measures of speech recognition. 2) Demographic/audiologic factors, particularly duration of deafness, duration of CI use, degree of residual hearing, and socioeconomic status, will impact performance on underlying information-processing functions, as assessed using process measures.

BACKGROUND

Clinicians and researchers rely heavily on endpoint product measures of accuracy in speech recognition to gauge patient outcomes postoperatively. However, these measures are primarily descriptive and were not designed to assess the underlying core information-processing operations that are used during speech recognition. In contrast, process measures reflect the integrity of elementary core subprocesses that are operative during behavioral tests using complex speech signals.

METHODS

Forty-two experienced adult CI users were tested using three product measures of speech recognition, along with four process measures of working memory capacity, inhibitory control, speed of lexical/phonological access, and nonverbal fluid reasoning. Demographic and audiologic factors were also assessed.

RESULTS

Scores on product measures were associated with core process measures of speed of lexical/phonological access and nonverbal fluid reasoning. After controlling for participant age, demographic and audiologic factors did not correlate with process measure scores.

CONCLUSION

Findings provide support for the important foundational roles of information processing operations in speech recognition outcomes of postlingually deaf patients who have received CIs.

Verbal Learning and Memory in Early-Implanted, Prelingually Deaf Adolescent and Adult Cochlear Implant Users

Purpose The purpose of this study was to investigate the information-processing strategies of early-implanted, prelingually deaf cochlear implant (CI) users with the California Verbal Learning Test-Second Edition (CVLT-II; Delis, Kramer, Kaplan, & Ober, 2000 ), a well-established normed measure of verbal learning and memory used in neuropsychological assessments of memory loss. Method Verbal learning and memory skills were compared in 20 older adolescent and young adult prelingually deaf long-term early-implanted CI users and their 24 normal hearing (NH) peers using the CVLT-II, a widely used multitrial free recall test of verbal learning and memory. Results On average, CI users recalled fewer words than their NH peers across the immediate, delayed, and cued recall trials of the CVLT-II but were comparable to their NH peers on yes/no recognition memory. CI users showed little evidence of semantic clustering of words during free recall but greater serial clustering compared to their NH peers, suggesting fundamental disturbances in automatic semantic activation of words from long-term memory. No differences were found in verbal memory between CI users and their NH peers on measures of retroactive interference and encoding/retrieval interactions. Performance on the 2nd word list of the CVLT-II (List B) and amount of semantic clustering of words during recall were correlated with sentence recognition in the CI group. Conclusion Study findings demonstrate significant differences in free recall performance and information-processing strategies that early-implanted, prelingually deaf CI users use to encode, organize, store, and retrieve spoken words in conventional verbal list learning paradigms, compared to their NH peers. Because verbal learning and memory are core foundational processes routinely used in daily functioning for a wide range of neurocognitive and language processing operations, these findings suggest potential domains for assessment and novel interventions to promote the development of optimal outcomes in prelingually deaf early-implanted long-term CI users.

Auditory recognition in toddlers with typical hearing and toddlers with hearing loss using the Hebrew version of the Mr. Potato Head Task

OBJECTIVE

This study describes the adaptation of the Mr. Potato Head Task into Hebrew and explores the development of word and sentence recognition in toddlers with typical hearing (TH) and toddlers with hearing loss (HL).

DESIGN

Toddlers manipulated Mr. Potato Head according to auditory instructions.

STUDY SAMPLE

One hundred and seventeen toddlers with TH and 28 toddlers with HL, age 23-48 months.

RESULTS

Internal consistency scores in TH toddlers - words: α = 0.85, sentences: α = 0.87; in toddlers with HL, words: α = 0.88; sentences: α = 0.84. The findings showed a clear upward trajectory in the TH toddlers, plateauing at age four. Toddlers with HL showed poorer performance in general, but exhibited a similar trajectory, albeit with greater individual variability. Toddlers with HL performed less well than age-matched toddlers with TH, but performed at the same level as toddlers with TH matched for hearing experience. Severity of HL was associated with performance level.

CONCLUSIONS

The Hebrew-adapted version can provide a developmental assessment of word and sentence recognition tasks in both groups of toddlers. These findings have important implications for toddlers with HL for whom assessment tools at the sentence level are rare.

Three challenges for future research on cochlear implants

Cochlear implants (CIs) often work very well for many children and adults with profound sensorineural (SNHL) hearing loss. Unfortunately, while many CI patients display substantial benefits in recognizing speech and understanding spoken language following cochlear implantation, a large number of patients achieve poor outcomes. Understanding and explaining the reasons for poor outcomes following implantation is a very challenging research problem that has received little attention despite the pressing clinical significance. In this paper, we discuss three challenges for future research on CIs. First, we consider the issue of individual differences and variability in outcomes following implantation. At the present time, we still do not have a complete and satisfactory account of the causal underlying factors that are responsible for the enormous individual differences and variability in outcomes. Second, we discuss issues related to the lack of preimplant predictors of outcomes. Very little prospective research has been carried out on the development of preimplant predictors that can be used to reliably identify CI candidates who may be at high risk for a poor outcome following implantation. Other than conventional demographics and hearing history, there are no prognostic tools available to predict speech recognition outcomes after implantation. Finally, we discuss the third challenge - what to do with a CI-user who has a poor outcome. We suggest that new research efforts need to be devoted to studying this neglected clinical population in greater depth to find out why they are doing poorly with their CI and what novel interventions and treatments can be developed to improve their speech recognition outcomes. Using these three challenges as objectives for future research on CIs, we suggest that the field needs to adopt a new narrative grounded in theory and methods from Cognitive Hearing Science and information processing theory. Without knowing which specific biological and neurocognitive factors are responsible for individual differences or understanding the underlying sensory and neurocognitive basis for variability in performance, it is impossible to select a specific approach to habilitation after a deaf adult or child receives a CI. Deaf adults and children who are performing poorly with their CIs are not a homogeneous group and may differ in many different ways from each other, reflecting the dysfunction of multiple brain systems associated with both congenital and acquired deafness. Hearing loss is not only an ear issue, it is also a brain issue too reflecting close links between perception and action and brain, body and world working together as a functionally integrated information processing system to support robust speech recognition and spoken language processing after implantation.

Verbal Working Memory in Children With Cochlear Implants

PURPOSE

Verbal working memory in children with cochlear implants and children with normal hearing was examined.

PARTICIPANTS

Ninety-three fourth graders (47 with normal hearing, 46 with cochlear implants) participated, all of whom were in a longitudinal study and had working memory assessed 2 years earlier.

METHOD

A dual-component model of working memory was adopted, and a serial recall task measured storage and processing. Potential predictor variables were phonological awareness, vocabulary knowledge, nonverbal IQ, and several treatment variables. Potential dependent functions were literacy, expressive language, and speech-in-noise recognition.

RESULTS

Children with cochlear implants showed deficits in storage and processing, similar in size to those at second grade. Predictors of verbal working memory differed across groups: Phonological awareness explained the most variance in children with normal hearing; vocabulary explained the most variance in children with cochlear implants. Treatment variables explained little of the variance. Where potentially dependent functions were concerned, verbal working memory accounted for little variance once the variance explained by other predictors was removed.

CONCLUSIONS

The verbal working memory deficits of children with cochlear implants arise due to signal degradation, which limits their abilities to acquire phonological awareness. That hinders their abilities to store items using a phonological code.

Visual-spatial sequence learning and memory in trained musicians

Previous research has shown that musicians have enhanced visual-spatial abilities and sensorymotor skills. As a result of their long-term musical training and their experience-dependent activities, musicians may learn to associate sensory information with fine motor movements. Playing a musical instrument requires musicians to rapidly translate musical symbols into specific sensory-motor actions while also simultaneously monitoring the auditory signals produced by their instrument. In this study, we assessed the visual-spatial sequence learning and memory abilities of long-term musicians. We recruited 24 highly trained musicians and 24 nonmusicians, individuals with little or no musical training experience. Participants completed a visual-spatial sequence learning task as well as receptive vocabulary, nonverbal reasoning, and short-term memory tasks. Results revealed that musicians have enhanced visual-spatial sequence learning abilities relative to nonmusicians. Musicians also performed better than nonmusicians on the vocabulary and nonverbal reasoning measures. Additional analyses revealed that the large group difference observed on the visualspatial sequencing task between musicians and nonmusicians remained even after controlling for vocabulary, nonverbal reasoning, and short-term memory abilities. Musicians' improved visualspatial sequence learning may stem from basic underlying differences in visual-spatial and sensorymotor skills resulting from long-term experience and activities associated with playing a musical instrument.

Learning and Memory Processes Following Cochlear Implantation: The Missing Piece of the Puzzle

At the present time, there is no question that cochlear implants (CIs) work and often work very well in quiet listening conditions for many profoundly deaf children and adults. The speech and language outcomes data published over the last two decades document quite extensively the clinically significant benefits of CIs. Although there now is a large body of evidence supporting the "efficacy" of CIs as a medical intervention for profound hearing loss in both children and adults, there still remain a number of challenging unresolved clinical and theoretical issues that deal with the "effectiveness" of CIs in individual patients that have not yet been successfully resolved. In this paper, we review recent findings on learning and memory, two central topics in the field of cognition that have been seriously neglected in research on CIs. Our research findings on sequence learning, memory and organization processes, and retrieval strategies used in verbal learning and memory of categorized word lists suggests that basic domain-general learning abilities may be the missing piece of the puzzle in terms of understanding the cognitive factors that underlie the enormous individual differences and variability routinely observed in speech and language outcomes following cochlear implantation.

Associations between speech understanding and auditory and visual tests of verbal working memory: effects of linguistic complexity, task, age, and hearing loss

Listeners with hearing loss commonly report having difficulty understanding speech, particularly in noisy environments. Their difficulties could be due to auditory and cognitive processing problems. Performance on speech-in-noise tests has been correlated with reading working memory span (RWMS), a measure often chosen to avoid the effects of hearing loss. If the goal is to assess the cognitive consequences of listeners’ auditory processing abilities, however, then listening working memory span (LWMS) could be a more informative measure. Some studies have examined the effects of different degrees and types of masking on working memory, but less is known about the demands placed on working memory depending on the linguistic complexity of the target speech or the task used to measure speech understanding in listeners with hearing loss. Compared to RWMS, LWMS measures using different speech targets and maskers may provide a more ecologically valid approach. To examine the contributions of RWMS and LWMS to speech understanding, we administered two working memory measures (a traditional RWMS measure and a new LWMS measure), and a battery of tests varying in the linguistic complexity of the speech materials, the presence of babble masking, and the task. Participants were a group of younger listeners with normal hearing and two groups of older listeners with hearing loss (n = 24 per group). There was a significant group difference and a wider range in performance on LWMS than on RWMS. There was a significant correlation between both working memory measures only for the oldest listeners with hearing loss. Notably, there were only few significant correlations among the working memory and speech understanding measures. These findings suggest that working memory measures reflect individual differences that are distinct from those tapped by these measures of speech understanding.

Deaf children with cochlear implants do not appear to use sentence context to help recognize spoken words

PURPOSE

The authors investigated the ability of deaf children with cochlear implants (CIs) to use sentence context to facilitate the perception of spoken words.

METHOD

Deaf children with CIs (n = 24) and an age-matched group of children with normal hearing (n = 31) were presented with lexically controlled sentences and were asked to repeat each sentence in its entirety. Performance was analyzed at each of 3 word positions of each sentence (first, second, and third key word).

RESULTS

Whereas the children with normal hearing showed robust effects of contextual facilitation-improved speech perception for the final words in a sentence-the deaf children with CIs on average showed no such facilitation. Regression analyses indicated that for the deaf children with CIs, Forward Digit Span scores significantly predicted accuracy scores for all 3 positions, whereas performance on the Stroop Color and Word Test, Children's Version (Golden, Freshwater, & Golden, 2003) predicted how much contextual facilitation was observed at the final word.

CONCLUSIONS

The pattern of results suggests that some deaf children with CIs do not use sentence context to improve spoken word recognition. The inability to use sentence context may be due to possible interactions between language experience and cognitive factors that affect the ability to successfully integrate temporal-sequential information in spoken language.

Speech intelligibility in deaf children after long-term cochlear implant use

PURPOSE

This study investigated long-term speech intelligibility outcomes in 63 prelingually deaf children, adolescents, and young adults who received cochlear implants (CIs) before age 7 (M = 2;11 [years;months], range = 0;8-6;3) and used their implants for at least 7 years (M = 12;1, range = 7;0-22;5).

METHOD

Speech intelligibility was assessed using playback methods with naïve, normal-hearing listeners.

RESULTS

Mean intelligibility scores were lower than scores obtained from an age- and nonverbal IQ-matched, normal-hearing control sample, although the majority of CI users scored within the range of the control sample. Our sample allowed us to investigate the contribution of several demographic and cognitive factors to speech intelligibility. CI users who used their implant for longer periods of time exhibited poorer speech intelligibility scores. Crucially, results from a hierarchical regression model suggested that this difference was due to more conservative candidacy criteria in CI users with more years of use. No other demographic variables accounted for significant variance in speech intelligibility scores beyond age of implantation and amount of spoken language experience (assessed by communication mode and family income measures).

CONCLUSION

Many factors that have been found to contribute to individual differences in language outcomes in normal-hearing children also contribute to long-term CI users' ability to produce intelligible speech.

Reduced procedural motor learning in deaf individuals

Studies in the deaf suggest that cross-modal neuroplastic changes may vary across modalities. Only a handful of studies have examined motor capacities in the profoundly deaf. These studies suggest the presence of deficits in manual dexterity and delays in movement production. As of yet, the ability to learn complex sequential motor patterns has not been explored in deaf populations. The aim of the present study was to investigate the procedural learning skills of deaf adults. A serial reaction-time task (SRTT) was performed by 18 deaf subjects and 18 matched controls to investigate possible motor alteration subsequent to auditory deprivation. Deaf participants had various degrees of hearing loss. Half of the experimental group were early deaf adults mostly using hearing aids, the remaining half were late-deaf adults using a cochlear implant (CI). Participants carried out a repeating 12-item sequence of key presses along with random blocks containing no repeating sequence. Non-specific and sequence-specific learning was analyzed in relation to individual features related to the hearing loss. The results revealed significant differences between groups in sequence-specific learning, with deaf subjects being less efficient than controls in acquiring sequence-specific knowledge. We interpret the results in light of cross-modal plasticity and the auditory scaffolding hypothesis.

Working memory in Farsi-speaking children with normal development and cochlear implant

AIM AND BACKGROUND

Working memory has an important role in language acquisition and development of cognition skills. The ability of encoding, storage and retrieval of phonological codes, as activities of working memory, acquired by audition sense. Children with cochlear implant experience a period that they are not able to perceive sounds. In order to assess the effect of hearing on working memory, we investigated working memory as a cognition skill in children with normal development and cochlear implant.

METHODS

Fifty students with normal hearing and 50 students with cochlear implant aged 5-7 years participated in this study. Children educated in the preschool, the first and second grades. Children with normal development were matched based on age, gender, and grade of education with cochlear implant. Two components of working memory including phonological loop and central executive were compared between two groups. Phonological loop assessed by nonword repetition task and forward digit span. To assess central executive component backward digit span was used. The developmental trend was studied in children with normal development and cochlear implant as well. The effect of age at implantation in children with cochlear implants on components of working memory was investigated.

RESULTS

There are significant differences between children with normal development and cochlear implant in all tasks that assess working memory (p < 0.001). The children's age at implantation was negatively correlated with all tasks (p < 0.001). In contrast, duration of usage of cochlear implant set was positively correlated with all tasks (p < 0.001). The comparison of working memory between different grades showed significant differences both in children with normal development and in children with cochlear implant (p < 0.05).

CONCLUSION

These results implied that children with cochlear implant may experience difficulties in working memory. Therefore, these children have problems in encoding, practicing, and repeating phonological units. The results also suggested working memory develops when the child grows up. In cochlear implant children, with decreasing age at implantation and increasing their experience in perceiving sound, working memory skills improved.

Language acquisition for deaf children: Reducing the harms of zero tolerance to the use of alternative approaches

Children acquire language without instruction as long as they are regularly and meaningfully engaged with an accessible human language. Today, 80% of children born deaf in the developed world are implanted with cochlear devices that allow some of them access to sound in their early years, which helps them to develop speech. However, because of brain plasticity changes during early childhood, children who have not acquired a first language in the early years might never be completely fluent in any language. If they miss this critical period for exposure to a natural language, their subsequent development of the cognitive activities that rely on a solid first language might be underdeveloped, such as literacy, memory organization, and number manipulation. An alternative to speech-exclusive approaches to language acquisition exists in the use of sign languages such as American Sign Language (ASL), where acquiring a sign language is subject to the same time constraints of spoken language development. Unfortunately, so far, these alternatives are caught up in an "either - or" dilemma, leading to a highly polarized conflict about which system families should choose for their children, with little tolerance for alternatives by either side of the debate and widespread misinformation about the evidence and implications for or against either approach. The success rate with cochlear implants is highly variable. This issue is still debated, and as far as we know, there are no reliable predictors for success with implants. Yet families are often advised not to expose their child to sign language. Here absolute positions based on ideology create pressures for parents that might jeopardize the real developmental needs of deaf children. What we do know is that cochlear implants do not offer accessible language to many deaf children. By the time it is clear that the deaf child is not acquiring spoken language with cochlear devices, it might already be past the critical period, and the child runs the risk of becoming linguistically deprived. Linguistic deprivation constitutes multiple personal harms as well as harms to society (in terms of costs to our medical systems and in loss of potential productive societal participation).

Enhancing speech discrimination through stimulus repetition

PURPOSE

To evaluate the effects of sequential and alternating repetition on speech-sound discrimination.

METHOD

Typically hearing adults' discrimination of 3 pairs of speech-sound contrasts was assessed at 3 signal-to-noise ratios using the change/no-change procedure. On change trials, the standard and comparison stimuli differ; on no-change trials, they are identical. Listeners were presented with 5 repetition conditions: 2 and 4 sequential repetitions of the standard followed by sequential repetitions of the comparison; 2 and 4 alternating presentations of the standard and comparison; and 1 repetition of the standard and comparison.

RESULTS

Both sequential and alternating repetition improved discrimination of the fricative and liquid contrasts, but neither was clearly superior to the other across the conditions.

CONCLUSIONS

The results support previous findings that increasing the number of fricative and liquid stimulus presentations improves discriminability and extends the findings to natural speech stimuli. Further, the effect of repetition is robust: Both sequential and alternating repetitions improve speech-sound discrimination, and few differences emerge between the two types of stimulus repetitions. The results have implications for evaluating the strength of the internal representation of speech stimuli in clinical populations believed to have a core deficit in phonological encoding, such as children with hearing loss.

Neurocognitive basis of implicit learning of sequential structure and its relation to language processing

The ability to learn and exploit environmental regularities is important for many aspects of skill learning, of which language may be a prime example. Much of such learning proceeds in an implicit fashion, that is, it occurs unintentionally and automatically and results in knowledge that is difficult to verbalize explicitly. An important research goal is to ascertain the underlying neurocognitive mechanisms of implicit learning abilities and understand its contribution to perception, language, and cognition more generally. In this article, we review recent work that investigates the extent to which implicit learning of sequential structure is mediated by stimulus-specific versus domain-general learning mechanisms. Although much of previous implicit learning research has emphasized its domain-general aspect, here we highlight behavioral work suggesting a modality-specific locus. Even so, our data also reveal that individual variability in implicit sequence learning skill correlates with performance on a task requiring sensitivity to the sequential context of spoken language, suggesting that implicit sequence learning to some extent is domain-general. Taking into consideration this behavioral work, in conjunction with recent imaging studies, we argue that implicit sequence learning and language processing are both complex, dynamic processes that partially share the same underlying neurocognitive mechanisms, specifically those that rely on the encoding and representation of phonological sequences.

Cognitive Predictors of Improvements in Adults’ Spoken Word Recognition Six Months after Cochlear Implant Activation

This study investigated whether cognitive measures obtained prior to cochlear implant surgery activation could predict improvements in spoken word recognition in adult cochlear implant recipients 6 months after activation. In addition to noncognitive factors identified by previous studies (i.e. younger age, shorter duration of hearing loss), the present results indicated that improvement in spoken word recognition was associated with higher verbal learning scores and better verbal working memory. Contrary to expectation, neither general cognitive ability nor processing speed was significantly correlated with outcome at 6 months. Multiple regression analyses revealed that a combination of verbal learning scores and lip-reading skill accounted for nearly 72% of the individual differences in improvement in spoken word recognition (i.e. the variance in spoken word recognition scores at 6 months that remained unexplained after controlling for baseline spoken word recognition scores). These findings have relevance for research on auditory processing with cochlear implants as well as implications for clinical interventions.

Behavioral inhibition and clinical outcomes in children with cochlear implants

OBJECTIVES/HYPOTHESIS

Individual speech and language outcomes of deaf children with cochlear implants (CIs) are quite varied. Individual differences in underlying cognitive functions may explain some of this variance. The current study investigated whether behavioral inhibition skills of deaf children were related to performance on a range of audiologic outcome measures.

DESIGN

Retrospective analysis of longitudinal data collected from prelingually and profoundly deaf children who used CIs.

METHODS

Behavioral inhibition skills were measured using a visual response delay task that did not require hearing. Speech and language measures were obtained from behavioral tests administered at 1-year intervals of CI use.

RESULTS

Female subjects showed higher response delay scores than males. Performance increased with length of CI use. Younger children showed greater improvement in performance as a function of device use than older children. No other subject variable had a significant effect on response delay score. A series of multiple regression analyses revealed several significant relations between delay task performance and open set word recognition, vocabulary, receptive language, and expressive language scores.

CONCLUSIONS

The present results suggest that CI experience affects visual information processing skills of prelingually deaf children. Furthermore, the observed pattern of relations suggests that speech and language processing skills are closely related to the development of response delay skills in prelingually deaf children with CIs. These relations may reflect underlying verbal encoding skills, subvocal rehearsal skills, and verbally mediated self-regulatory skills. Clinically, visual response delay tasks may be useful in assessing behavioral and cognitive development in deaf children after implantation.