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Auditory Brain Development in Children with Hearing Loss – Part Two

Objectives:This longitudinal study followed the language development of children who received the combination of early (5 to 18 months) and simultaneous bilateral cochlear implants (CIs) throughout the first 6 years after implantation. It examined the trajectories of their language development and identified factors associated with language outcomes.Design:Participants were 21 Norwegian children who received bilateral CIs between the ages of 5 and 18 mo and 21 children with normal hearing (NH) who were matched to the children with CIs on age, sex, and maternal education. The language skills of these two groups were compared at 10 time points (3, 6, 9, 12, 18, 24, 36, 48, 60, and 72 months after implantation) using parent reports and standardized measures of general language skills, vocabulary, and grammar. In addition, assessments were made of the effects of age at CI activation, speech recognition abilities, and mothers’ education on language outcomes 6 years after implantation.Results:During the first 4 years after implantation, the gap in general expressive and receptive language abilities between children with CIs and children with NH gradually closed. While at the initial five to six assessments (3 to 36 months after implantation), significant differences between children with CIs and children with NH were observed; at 4 years after implantation, there were no longer any significant group differences in general language skills and most children with CIs achieved scores within 1 SD of the tests’ normative means. From 2 to 3 years after implantation onward, expressive vocabulary and receptive grammar skills of children with CIs were similar to those of the reference group. However, from 4 years after implantation until the end of the observation period, 6 years after implantation, expressive grammar skills of children with CIs were lower than those of children with NH. In addition, a gap in receptive vocabulary appeared and grew increasingly larger from 4 to 6 years postimplantation. At the final assessment, the children with CIs had an average receptive vocabulary score around 1 SD below the normative mean. Regression analysis indicated that the children’s language outcomes at 6 years after implantation were related to their speech recognition skills, age at CI activation, and maternal education.Conclusions:In the first 4 years after implantation, the language performance of children with CIs became increasingly similar to that of their NH peers. However, between 4 and 6 years after implantation, there were indications of challenges with certain aspects of language, specifically receptive vocabulary and expressive grammar. Because these challenges first appeared after the 4-year assessment, the findings underline the importance of long-term language intervention to increase the chances of a continued language development comparable to that of NH peers. They also indicate that there is a need for comprehensive longitudinal studies of the language development of children with CIs beyond 4 years after implantation.

Today, cochlear implant provides an appropriate opportunity for the development of speech and language in children. In some studies, the age of children at the time of surgery has been stated as the most important factor in the development of speech and language of children after cochlear implant, while in other studies factors, including participation in rehabilitation programs, parental educational level, and lack of other disability have been regarded as key factors in the development of speech and language in these children. This review aims to assess the conducted studies in Iran to identify factors contributing to improving the auditory perception, language, and other skills in children with cochlear implants in comparison to children with normal hearing. The purpose of this study is to review the results of studies conducted on speech and language abilities in children with cochlear implant compared to the normal group in Iran. Directory of Open Access Journals, Google Scholar, PubMed (NLM), LISTA (EBSCO), and Web of Science have been searched. cochlear implants in deaf children before language learning results in the acquisition of speech and language skills in children. Timely detection of hearing impairment, early implantation, duration of hearing, and parental involvement in the rehabilitation process are important factors that affect the development of speech and language. The child's age at the time of implantation, continued participation in rehabilitation programs and the lack of associated problems directly impact the development of auditory perception, speech and language of children with cochlear implant while family education level indirectly impacts this developmental process.

The principal goal of this study was to investigate the relationship between language and literacy (i.e., reading and writing) skills in pediatric cochlear implant users. A peripheral objective was to identify the children's skills that were in need of remediation and subsequently to provide suggestions for remedial programming. It was predicted that the robust language skills often associated with children who have cochlear implant experience would facilitate the development of literacy skills. It was further proposed that the language and literacy skills of pediatric cochlear implant users would approximate the language and literacy skills of children with normal hearing. Sixteen pediatric cochlear implant users' language and literacy skills were evaluated and then compared with a reference group of 16 age-matched, normal-hearing children. All 32 participants were educated in mainstream classes within the public school system in the Midwest. The "Sentence Formulation" and "Concepts and Directions" subtests of the Clinical Evaluation of Language Fundamentals-3 test were used to evaluate receptive and expressive language skills. Reading comprehension was evaluated with the "Paragraph Comprehension" subtest of the Woodcock Reading Mastery Test. Performance measures for the writing analyses included productivity, complexity and grammaticality measures. Children with cochlear implants performed within 1 SD of the normal-hearing, age-matched children on measures of language comprehension, reading comprehension and writing accuracy. However, the children with cochlear implants performed significantly poorer than the children with normal hearing on the expressive "Sentence Formulation" subtest. The cochlear implant users also produced fewer words on the written narrative task than did the normal-hearing children, although there was not a significant difference between groups with respect to total words per clause. Furthermore there was a strong correlation between language performance and reading performance, as well as language performance and total words produced on the written performance measure for the children using cochlear implants. The results of this study suggest that the language skills of pediatric cochlear implant users are related to and correlated with the development of literacy skills within these children. Consequently, the performance of the cochlear implant users, on various language and literacy measures, compared favorably to an age-matched group of children with normal hearing. There were significant differences in the ability of the cochlear implant users to correctly utilize grammatical structures such as conjunctions and correct verb forms when they were required to formulate written and oral sentences. Given this information, it would be appropriate for their educational or remedial language programs to emphasize the use and development of these structures.

Cochlear implantation (CI) in prelingually deafened children has been shown to be an effective intervention for developing language and reading skill. However, there is a substantial proportion of the children receiving CI who struggle with language and reading. The current study-one of the first to implement electrical source imaging in CI population was designed to identify the neural underpinnings in two groups of CI children with good and poor language and reading skill. Data using high density electroencephalography (EEG) under a resting state condition was obtained from 75 children, 50 with CIs having good (HL) or poor language skills (LL) and 25 normal hearing (NH) children. We identified coherent sources using dynamic imaging of coherent sources (DICS) and their effective connectivity computing time-frequency causality estimation based on temporal partial directed coherence (TPDC) in the two CI groups compared to a cohort of age and gender matched NH children. Sources with higher coherence amplitude were observed in three frequency bands (alpha, beta and gamma) for the CI groups when compared to normal hearing children. The two groups of CI children with good (HL) and poor (LL) language ability exhibited not only different cortical and subcortical source profiles but also distinct effective connectivity between them. Additionally, a support vector machine (SVM) algorithm using these sources and their connectivity patterns for each CI group across the three frequency bands was able to predict the language and reading scores with high accuracy. Increased coherence in the CI groups suggest overall that the oscillatory activity in some brain areas become more strongly coupled compared to the NH group. Moreover, the different sources and their connectivity patterns and their association to language and reading skill in both groups, suggest a compensatory adaptation that either facilitated or impeded language and reading development. The neural differences in the two groups of CI children may reflect potential biomarkers for predicting outcome success in CI children.

ObjectiveTo examine whether age at cochlear implantation or duration of implant use is associated with speech, language, and reading skills exhibited at age 8 to 9 years in children who underwent implantation by age 5 years.DesignPerformance outcomes in speech perception, speech production, language, and reading were examined in terms of the age at which children first received a cochlear implant (2, 3, or 4 years), the age they received an updated (Spectra) processor, and the duration of use of an implant and an updated processor.SettingData collection was conducted at summer research camps held over 4 consecutive years to maximize the number of children available at a specific age (8-9 years). Children were tested individually by experienced examiners, and their parents and therapists provided background and educational history information.ParticipantsA total of 181 children from 33 different states and 5 Canadian provinces who received a cochlear implant by age 5 years were tested. A subsample of 133 children with performance IQ scores of 80 or greater and onset of deafness at birth were selected for the age-at-implantation analysis. Another subsample of 39 children with deafness acquired by age 3 years was also examined.Outcome MeasuresA battery of tests of speech perception, speech production, language, and reading was administered to each child and reduced to a single factor score for each skill.ResultsCorrelation coefficients between age at implantation and duration of use did not reach significance for any of the outcome skills measured. Age at which the updated speech processor (Spectra) was fitted was significantly related to speech production outcome (earlier use of an updated processor was associated with greater speech intelligibility) but not to any other skill area. However, more of the children who underwent implantation at age 2 years (43%) achieved combined speech and language skills commensurate with their age-matched peers with normal hearing than did children who underwent implantation at age 4 years (16%). Furthermore, normal speech and language skills were documented in 80% of children who lost hearing after birth and who underwent implantation within a year of onset of deafness.ConclusionsFor children who receive a cochlear implant between the ages of 2 and 4 years, early cochlear implantation does not ensure better speech perception, speech production, language, or reading skills. However, greater speech and language proficiency may be expected from children who exhibit normal hearing for even a brief period after birth and receive a cochlear implant shortly after losing their hearing. Further research examining the benefits of cochlear implantation before age 2 years will help families and clinicians better understand the time-sensitive nature of the decision to conduct cochlear implant surgery.

Early intervention through hearing aids (HAs) and cochlear implants (CIs) aims to reduce the negative effects of childhood hearing loss and to promote optimal communication development over time. The primary goal of this study was to examine the communication outcomes of children with CIs and children with HAs at age 4 to 5 yrs and to consider their spoken language skills relative to a group of typically developing hearing peers. In this multicenter observational study, communication results were obtained for a total of 88 children at age 4 to 5 yrs. Participants were recruited from three clinical programs in two cities in the province of Ontario, Canada. This study was undertaken shortly after the introduction of a new provincial population screening initiative and included both children who were screened and not screened for hearing loss. The study sample comprised 51 children with sensorineural hearing loss and 37 children with normal hearing. Of the 51 children with hearing loss, 26 used CIs and 25 used HAs. The degree of hearing loss ranged from mild to profound. All children were enrolled in rehabilitation programs focused on oral language development. Children's language skills were assessed with an extensive battery of child- and parent-administered speech and language measures. Assessment of language skills showed no significant differences between the children with severe to profound hearing loss using CIs and children with varying degrees of hearing loss using HAs. However, children with HAs showed better articulation skills. Overall, both groups of children obtained scores on communication measures that were lower than their hearing peers. The number of children with hearing loss who obtained spoken speech-language scores within 1 SD of normative populations ranged from 65 to 86% depending on the test measure. Children with average hearing loss of 70 dB HL or better generally obtained scores on all measures in line with those of age-matched norms while scores were quite variable for children with severe and profound hearing loss. Factors influencing performance in children with hearing loss included degree of hearing loss (pure-tone average) and parent education. Age at diagnosis of hearing loss was not a significant predictor of speech-language outcomes in this study. Results indicated that overall, children with all degrees of hearing loss who were fit with hearing technology and who received auditory-based rehabilitation services during the preschool years demonstrated the potential to develop spoken language communication skills. As a group, children with CIs and children with HAs did not differ significantly on language abilities although there were differences in articulation skills. Their performance at age 4 to 5 yrs was delayed compared with a group of hearing peers. The findings reinforce the need for research to identify factors that are likely to lead to age-appropriate communication skills for preschool-age children with hearing loss.

<p dir="ltr"><b>Purpose</b>: The long-term effects of early cochlear implantation (CI) on higher- level language and cognitive abilities in adolescence are not well understood. This thesis examined whether adolescents and young adults with early CI show language and cognitive skills comparable to peers with typical hearing (TH), focusing on executive functions, word fluency, and metaphor comprehension, and explored the influence of age at implantation.</p><p dir="ltr"><b>Methods</b>: Participants included 43 adolescents and young adults with cochlear implants (mean age 16.9 years, mean implantation age 15.6 months) and 27 peers with typical hearing (mean age 14.9 years). Cognitive and language abilities were assessed using standardized tests and experimental tasks. Executive functions and communicative skills were also evaluated via self- and parent-report questionnaires. Metaphor comprehension was assessed with a newly developed multiple-choice task. Word fluency tasks were used to measure semantic and phonological retrieval strategies. For the CI group, longitudinal vocabulary and word fluency data (ages 5-15) were obtained from medical records and analyzed using linear mixed models to explore the effects of age and age at implantation.</p><p dir="ltr"><b>Results</b>: Participants with CI had significantly lower phonological working memory compared to peers with TH but performed similarly on all other measures. Earlier age at implantation was moderately associated with better phonological working memory and metaphor comprehension. Additionally, later- implanted participants relied more on semantic clustering strategies during word retrieval tasks. Associations between both executive functions and vocabulary measures, as well as between metaphor comprehension and relevant control variables, were less widespread in the CI group.</p><p dir="ltr"><b>Conclusions</b>: Early-implanted adolescents and young adults show cognitive and language outcomes similar to peers with typical hearing. Early auditory access supports higher-level skills, including metaphor comprehension and phonological working memory. Compensatory strategies may support language processing in individuals with cochlear implants, though further research is needed to understand these mechanisms.</p><h3 dir="ltr">List of scientific papers</h3><p dir="ltr">I. Löfkvist U, <b>Dahlby-Skoog M,</b> Persson A, Asp F, Verrecchia L, Gripenberg S, Karpeta N, Eklöf M, Karltorp E. Teenagers and Young Adults with Cochlear Implants: A Multidisciplinary Follow-Up Study Approach and Baseline Characteristics. Audiol Res. 2025 Feb 12;15(1):16. <a href="https://doi.org/10.3390/audiolres15010016">https://doi.org/10.3390/audiolres15010016<br></a><br></p><p dir="ltr">II. <b>Dahlby-Skoog M,</b> Kalandadze T, Karltorp E, Lyxell B, Löfkvist U. Hearing Early Opens More Doors: Long-Term Effects of Age at Implantation on Metaphor Comprehension in Adolescents and Young Adults with Cochlear Implants. J Speech Lang Hear Res. 2025 Mar 5;68(3):1105-1125. <a href="https://doi.org/10.1044/2024_jslhr-24-00480" rel="noreferrer" target="_blank">https://doi.org/10.1044/2024_jslhr-24-00480</a></p><p dir="ltr">III. Early Cochlear Implantation Supports Phonological Working Memory in Adolescents and Young Adults with Otherwise Typical Executive Functions. [Manuscript]</p><p dir="ltr">IV. Lexical Retrieval Strategies and Vocabulary Development in Adolescents with Cochlear Implants. [Manuscript]</p>

<p dir="ltr"><b>Purpose</b>: The long-term effects of early cochlear implantation (CI) on higher- level language and cognitive abilities in adolescence are not well understood. This thesis examined whether adolescents and young adults with early CI show language and cognitive skills comparable to peers with typical hearing (TH), focusing on executive functions, word fluency, and metaphor comprehension, and explored the influence of age at implantation.</p><p dir="ltr"><b>Methods</b>: Participants included 43 adolescents and young adults with cochlear implants (mean age 16.9 years, mean implantation age 15.6 months) and 27 peers with typical hearing (mean age 14.9 years). Cognitive and language abilities were assessed using standardized tests and experimental tasks. Executive functions and communicative skills were also evaluated via self- and parent-report questionnaires. Metaphor comprehension was assessed with a newly developed multiple-choice task. Word fluency tasks were used to measure semantic and phonological retrieval strategies. For the CI group, longitudinal vocabulary and word fluency data (ages 5-15) were obtained from medical records and analyzed using linear mixed models to explore the effects of age and age at implantation.</p><p dir="ltr"><b>Results</b>: Participants with CI had significantly lower phonological working memory compared to peers with TH but performed similarly on all other measures. Earlier age at implantation was moderately associated with better phonological working memory and metaphor comprehension. Additionally, later- implanted participants relied more on semantic clustering strategies during word retrieval tasks. Associations between both executive functions and vocabulary measures, as well as between metaphor comprehension and relevant control variables, were less widespread in the CI group.</p><p dir="ltr"><b>Conclusions</b>: Early-implanted adolescents and young adults show cognitive and language outcomes similar to peers with typical hearing. Early auditory access supports higher-level skills, including metaphor comprehension and phonological working memory. Compensatory strategies may support language processing in individuals with cochlear implants, though further research is needed to understand these mechanisms.</p><h3 dir="ltr">List of scientific papers</h3><p dir="ltr">I. Löfkvist U, <b>Dahlby-Skoog M,</b> Persson A, Asp F, Verrecchia L, Gripenberg S, Karpeta N, Eklöf M, Karltorp E. Teenagers and Young Adults with Cochlear Implants: A Multidisciplinary Follow-Up Study Approach and Baseline Characteristics. Audiol Res. 2025 Feb 12;15(1):16. <a href="https://doi.org/10.3390/audiolres15010016">https://doi.org/10.3390/audiolres15010016<br></a><br></p><p dir="ltr">II. <b>Dahlby-Skoog M,</b> Kalandadze T, Karltorp E, Lyxell B, Löfkvist U. Hearing Early Opens More Doors: Long-Term Effects of Age at Implantation on Metaphor Comprehension in Adolescents and Young Adults with Cochlear Implants. J Speech Lang Hear Res. 2025 Mar 5;68(3):1105-1125. <a href="https://doi.org/10.1044/2024_jslhr-24-00480" rel="noreferrer" target="_blank">https://doi.org/10.1044/2024_jslhr-24-00480</a></p><p dir="ltr">III. Early Cochlear Implantation Supports Phonological Working Memory in Adolescents and Young Adults with Otherwise Typical Executive Functions. [Manuscript]</p><p dir="ltr">IV. Lexical Retrieval Strategies and Vocabulary Development in Adolescents with Cochlear Implants. [Manuscript]</p>

To examine whether age at cochlear implantation or duration of implant use is associated with speech, language, and reading skills exhibited at age 8 to 9 years in children who underwent implantation by age 5 years. Performance outcomes in speech perception, speech production, language, and reading were examined in terms of the age at which children first received a cochlear implant (2, 3, or 4 years), the age they received an updated (Spectra) processor, and the duration of use of an implant and an updated processor. Data collection was conducted at summer research camps held over 4 consecutive years to maximize the number of children available at a specific age (8-9 years). Children were tested individually by experienced examiners, and their parents and therapists provided background and educational history information. A total of 181 children from 33 different states and 5 Canadian provinces who received a cochlear implant by age 5 years were tested. A subsample of 133 children with performance IQ scores of 80 or greater and onset of deafness at birth were selected for the age-at-implantation analysis. Another subsample of 39 children with deafness acquired by age 3 years was also examined. A battery of tests of speech perception, speech production, language, and reading was administered to each child and reduced to a single factor score for each skill. Correlation coefficients between age at implantation and duration of use did not reach significance for any of the outcome skills measured. Age at which the updated speech processor (Spectra) was fitted was significantly related to speech production outcome (earlier use of an updated processor was associated with greater speech intelligibility) but not to any other skill area. However, more of the children who underwent implantation at age 2 years (43%) achieved combined speech and language skills commensurate with their age-matched peers with normal hearing than did children who underwent implantation at age 4 years (16%). Furthermore, normal speech and language skills were documented in 80% of children who lost hearing after birth and who underwent implantation within a year of onset of deafness. For children who receive a cochlear implant between the ages of 2 and 4 years, early cochlear implantation does not ensure better speech perception, speech production, language, or reading skills. However, greater speech and language proficiency may be expected from children who exhibit normal hearing for even a brief period after birth and receive a cochlear implant shortly after losing their hearing. Further research examining the benefits of cochlear implantation before age 2 years will help families and clinicians better understand the time-sensitive nature of the decision to conduct cochlear implant surgery.

A major issue in the rehabilitation of children with cochlear implants (CIs) is unexplained variance in their language skills, where many of them lag behind children with normal hearing (NH). Here, we assess links between generative language skills and the perception of prosodic stress, and with musical and parental activities in children with CIs and NH. Understanding these links is expected to guide future research and toward supporting language development in children with a CI. Twenty-one unilaterally and early-implanted children and 31 children with NH, aged 5 to 13, were classified as musically active or nonactive by a questionnaire recording regularity of musical activities, in particular singing, and reading and other activities shared with parents. Perception of word and sentence stress, performance in word finding, verbal intelligence (Wechsler Intelligence Scale for Children (WISC) vocabulary), and phonological awareness (production of rhymes) were measured in all children. Comparisons between children with a CI and NH were made against a subset of 21 of the children with NH who were matched to children with CIs by age, gender, socioeconomic background, and musical activity. Regression analyses, run separately for children with CIs and NH, assessed how much variance in each language task was shared with each of prosodic perception, the child's own music activity, and activities with parents, including singing and reading. All statistical analyses were conducted both with and without control for age and maternal education. Musically active children with CIs performed similarly to NH controls in all language tasks, while those who were not musically active performed more poorly. Only musically nonactive children with CIs made more phonological and semantic errors in word finding than NH controls, and word finding correlated with other language skills. Regression analysis results for word finding and VIQ were similar for children with CIs and NH. These language skills shared considerable variance with the perception of prosodic stress and musical activities. When age and maternal education were controlled for, strong links remained between perception of prosodic stress and VIQ (shared variance: CI, 32%/NH, 16%) and between musical activities and word finding (shared variance: CI, 53%/NH, 20%). Links were always stronger for children with CIs, for whom better phonological awareness was also linked to improved stress perception and more musical activity, and parental activities altogether shared significantly variance with word finding and VIQ. For children with CIs and NH, better perception of prosodic stress and musical activities with singing are associated with improved generative language skills. In addition, for children with CIs, parental singing has a stronger positive association to word finding and VIQ than parental reading. These results cannot address causality, but they suggest that good perception of prosodic stress, musical activities involving singing, and parental singing and reading may all be beneficial for word finding and other generative language skills in implanted children.

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Background: Cochlear implants (CIs) restore partial hearing to deaf children, promoting the development of spoken language skills. However, because of reduced auditory and language experience, children who receive CIs are at risk for delays not only in language skills but also in language-related neurocognitive skills such as verbal working memory (VWM - the ability to retain language information in immediate memory concurrently with other cognitive processing). Although VWM delays in children with CIs are well-documented, the foundational processes underlying these delays are less clear. This study investigated the hypotheses that slower speed of information processing during VWM tasks contributes to VWM delays in CI users and that this slower information processing speed is associated with spoken language outcomes. Methods: 25 early-implanted, prelingually-deaf children with CIs and 25 normal-hearing (NH) peers completed tests of VWM, neurocognitive, and speech-language functioning. Speed of information processing during the VWM test was assessed by measuring response latency and average pause duration. Results: Children with CIs showed poorer VWM scores than NH peers, but the groups did not differ on response latencies or pause durations. Response latencies were significantly correlated with VWM capacity, speech, and language outcomes in both groups. Conclusion: Speed of information processing in VWM was similar for children with CIs and NH. In both groups, shorter response latencies (faster speed of execution of the cognitive operations of working memory) were associated with better neurocognitive and spoken language outcomes. In the CI sample, pause durations were inconsistently associated with VWM and language outcomes. Clinical Policy Impact and Implications: Speed of information processing for VWM is associated with core neurocognitive and spoken language outcomes for children with CIs and should be a routine target of assessment and intervention post-implantation.