Central auditory development: evidence from CAEP measurements in children fit with cochlear implants

In normal-hearing children the latency of the P1 component of the cortical evoked response to sound varies as a function of age and, thus, can be used as a biomarker for maturation of central auditory pathways. We assessed P1 latency in 245 congenitally deaf children fit with cochlear implants following various periods of auditory deprivation. If children experience less than 3.5 years of auditory deprivation before implantation, P1 latencies fall into the range of normal following 3-6 months of electrical stimulation. Children who experience greater than 7 years of deprivation, however, generally do not develop normal P1 latencies even after years of stimulation. Moreover, the waveforms for these patients can be markedly abnormal. Cortical reorganization stimulated by deprivation is likely to be a significant factor in both variation in the latency and morphology of the cortical evoked response to sound for children fit with a cochlear implant and variation in the development of oral speech and language function. LEARNING OUTCOMES: The reader will be introduced to research using cortical evoked responses (CAEPs), positron emission tomography (PET) scans and in-depth recording from the auditory cortex of congenitally deaf cats that converges on the existence of a sensitive period for the development of central auditory pathways in children. The reader will also be provided with two case studies that illustrate the use of the P1 response as biomarker for development of central auditory pathways. Finally, suggestions for future research will be provided.     

Central auditory maturation and babbling development in infants with cochlear implants

OBJECTIVE: To examine the relationship between the maturation of central auditory pathways and the development of canonical (speechlike) babbling in infants with cochlear implants. DESIGN: Comparison of the latencies of the P1 cortical auditory evoked potential and vocalizations produced by subjects before they were fitted with a cochlear implant and at several time points within the first year after implantation. SUBJECTS: Two congenitally deaf children who were implanted with a multichannel cochlear implant at ages 13 and 14 months. INTERVENTIONS: P1 response latencies were recorded in response to a /ba/ stimulus before implantation and at several time points following implantation. Vocalizations produced by the subjects while interacting with their caregiver were audiorecorded twice before implantation and at monthly sessions following implantation. RESULTS: Subjects showed a rapid decrease in P1 latencies resulting in normal P1 latencies within about 3 months after implantation. Before implantation, the vocalizations were primarily of a precanonical nature. After 3 months' experience with the implants, the proportion of canonical vocalizations increased dramatically relative to the number of precanonical utterances. CONCLUSIONS: Results of this study suggest that the development of P1 response latencies and the development of early communicative behaviors may follow a similar developmental trajectory in children implanted early. Although preliminary, these findings indicate that the development of early communicative behaviors following implantation may be positively influenced by the rate of plastic changes in central auditory pathways.     

The influence of a sensitive period on central auditory development in children with unilateral and bilateral cochlear implants

We examined the longitudinal development of the cortical auditory evoked potential (CAEP) in 21 children who were fitted with unilateral cochlear implants and in two children who were fitted with bilateral cochlear implants either before age 3.5 years or after age 7 years. The age cut-offs (<3.5 years for early-implanted and >7 years for late-implanted) were based on the sensitive period for central auditory development described in [Ear Hear. 23 (6), 532.] Our results showed a fundamentally different pattern of development of CAEP morphology and P1 cortical response latency for early- and late-implanted children. Early-implanted children and one child who received bilateral implants by age 3.5 years showed rapid development in CAEP waveform morphology and P1 latency. Late-implanted children showed aberrant waveform morphology and significantly slower decreases in P1 latency postimplantation. In the case of a child who received his first implant by age 3.5 years and his second implant after age 7 years, CAEP responses elicited by the second implant were similar to late-implanted children. Our results are consistent with animal models of central auditory development after implantation and confirm the presence of a relatively brief sensitive period for central auditory development in young children.     

Central auditory maturation and behavioral outcome in children with auditory neuropathy spectrum disorder who use cochlear implants

Abstract

Objective: We examined cortical auditory development and behavioral outcomes in children with ANSD fitted with cochlear implants (CI). Design: Cortical maturation, measured by P1 cortical auditory evoked potential (CAEP) latency, was regressed against scores on the infant toddler meaningful auditory integration scale (IT-MAIS). Implantation age was also considered in relation to CAEP findings. Study sample: Cross-sectional and longitudinal samples of 24 and 11 children, respectively, with ANSD fitted with CIs. Results: P1 CAEP responses were present in all children after implantation, though previous findings suggest that only 50–75% of ANSD children with hearing aids show CAEP responses. P1 CAEP latency was significantly correlated with participants’ IT-MAIS scores. Furthermore, more children implanted before age two years showed normal P1 latencies, while those implanted later mainly showed delayed latencies. Longitudinal analysis revealed that most children showed normal or improved cortical maturation after implantation. Conclusion: Cochlear implantation resulted in measureable cortical auditory development for all children with ANSD. Children fitted with CIs under age two years were more likely to show age-appropriate CAEP responses within six months after implantation, suggesting a possible sensitive period for cortical auditory development in ANSD. That CAEP responses were correlated with behavioral outcome highlights their clinical decision-making utility.     

A longitudinal study of the bilateral benefit in children with bilateral cochlear implants

Objective: To study the development of the bilateral benefit in children using bilateral cochlear implants by measurements of speech recognition and sound localization. Design: Bilateral and unilateral speech recognition in quiet, in multi-source noise, and horizontal sound localization was measured at three occasions during a two-year period, without controlling for age or implant experience. Longitudinal and cross-sectional analyses were performed. Results were compared to cross-sectional data from children with normal hearing. Study sample: Seventy-eight children aged 5.1–11.9 years, with a mean bilateral cochlear implant experience of 3.3 years and a mean age of 7.8 years, at inclusion in the study. Thirty children with normal hearing aged 4.8–9.0 years provided normative data. Results: For children with cochlear implants, bilateral and unilateral speech recognition in quiet was comparable whereas a bilateral benefit for speech recognition in noise and sound localization was found at all three test occasions. Absolute performance was lower than in children with normal hearing. Early bilateral implantation facilitated sound localization. Conclusions: A bilateral benefit for speech recognition in noise and sound localization continues to exist over time for children with bilateral cochlear implants, but no relative improvement is found after three years of bilateral cochlear implant experience.     

Jumpstarting auditory learning in children with cochlear implants through music experiences

Abstract

Musical experiences are a valuable part of the lives of children with cochlear implants (CIs). In addition to the pleasure, relationships and emotional outlet provided by music, it serves to enhance or ‘jumpstart’ other auditory and cognitive skills that are critical for development and learning throughout the lifespan. Musicians have been shown to be ‘better listeners’ than non-musicians with regard to how they perceive and process sound. A heuristic model of music therapy is reviewed, including six modulating factors that may account for the auditory advantages demonstrated by those who participate in music therapy. The integral approach to music therapy is described along with the hybrid approach to pediatric language intervention. These approaches share the characteristics of placing high value on ecologically valid therapy experiences, i.e., engaging in ‘real’ music and ‘real’ communication. Music and language intervention techniques used by the authors are presented. It has been documented that children with CIs consistently have lower music perception scores than do their peers with normal hearing (NH). On the one hand, this finding matters a great deal because it provides parameters for setting reasonable expectations and highlights the work still required to improve signal processing with the devices so that they more accurately transmit music to CI listeners. On the other hand, the finding might not matter much if we assume that music, even in its less-than-optimal state, functions for CI children, as for NH children, as a developmental jumpstarter, a language-learning tool, a cognitive enricher, a motivator, and an attention enhancer.     

Sequential bilateral cochlear implantation in children: development of the primary auditory abilities of bilateral stimulation

The advantages of sequential bilateral cochlear implantation were assessed in 29 children with a severe to profound hearing loss. The effect of age at second implantation and the effect of duration of bilateral implant use on the outcomes in speech perception and directional hearing were investigated. The children received their second cochlear implant at an age ranging from 2.8 to 8.5 years. Measurements were carried out preoperatively and postoperatively after 6, 12 and 24 months of bilateral implant use. A matched control group of 9 children with a unilateral implant were also measured over time and were compared with the study group after 12 and 24 months. Speech reception in both quiet and in noise and lateralization were measured. After 24 months, a minimum audible angle task was carried out. Bilateral advantages with regard to speech reception in quiet and in noise were already present after 6 months of bilateral implant use and improved thereafter. After 24 months, speech reception in noise had significantly improved with bilateral implants compared to that of children with a unilateral implant. The percentage of children that could accurately lateralize increased from 57% after 6 months to 83% after 24 months. With regard to the minimum audible angle task, loudspeakers were placed on average at ±42°. Age at second implantation did not have an influence on all outcomes. From the results it can be concluded that the advantages of bilateral hearing occur after sequential bilateral implantation and that age at second implantation does not influence the amount of bilateral advantage. Furthermore, it can be concluded that longer periods of bilateral implant use lead to greater bilateral advantages.     

Sound-direction identification with bilateral cochlear implants

OBJECTIVE: The purpose of this study was to compare the accuracy of sound-direction identification in the horizontal plane by bilateral cochlear implant users when localization was measured with pink noise and with speech stimuli. DESIGN: Eight adults who were bilateral users of Nucleus 24 Contour devices participated in the study. All had received implants in both ears in a single surgery. Sound-direction identification was measured in a large classroom by using a nine-loudspeaker array. Localization was tested in three listening conditions (bilateral cochlear implants, left cochlear implant, and right cochlear implant), using two different stimuli (a speech stimulus and pink noise bursts) in a repeated-measures design. RESULTS: Sound-direction identification accuracy was significantly better when using two implants than when using a single implant. The mean root-mean-square error was 29 degrees for the bilateral condition, 54 degrees for the left cochlear implant, and 46.5 degrees for the right cochlear implant condition. Unilateral accuracy was similar for right cochlear implant and left cochlear implant performance. Sound-direction identification performance was similar for speech and pink noise stimuli. CONCLUSIONS: The data obtained in this study add to the growing body of evidence that sound-direction identification with bilateral cochlear implants is better than with a single implant. The similarity in localization performance obtained with the speech and pink noise supports the use of either stimulus for measuring sound-direction identification.     

Spatial hearing in a child with auditory neuropathy spectrum disorder and bilateral cochlear implants

Abstract

Objective: The neural dys-synchrony associated with auditory neuropathy spectrum disorder (ANSD) causes a temporal impairment that could degrade spatial hearing, particularly sound localization accuracy (SLA) and spatial release from masking (SRM). Unilateral cochlear implantation has become an accepted treatment for ANSD but treatment options for the contralateral ear remain controversial. We report spatial hearing measures in a child with ANSD before and after receiving a second cochlear implant (CI). Study sample: An 11-year-7-month old boy with ANSD and expressive and receptive language delay received a second CI eight years after his first implant. Design: The SLA and SRM were measured four months before sequential bilateral CIs (with the contralateral ear plugged and unplugged), and after nine months using both CIs. Results: Testing done before the second CI, with the first CI alone, suggested that residual hearing in the contralateral ear contributed to sound localization accuracy, but not word recognition in quiet or noise. Nine-months after receiving a second CI, SLA improved by 12.76° and SRM increased to 3.8–4.2 dB relative to pre-operative performance. Results were compared to published outcomes for children with bilateral CIs. Conclusions: The addition of a second CI in this child with ANSD improved spatial hearing.     

Language development in children after receiving bilateral cochlear implants between 5 and 18 months

Objective

The objective of this study was to examine receptive and expressive language development in children who received simultaneous bilateral cochlear implants (CIs) between 5 and 18 months of age and to compare the results with language development in chronologically age-matched children with normal hearing.

Methods

The study used a prospective, longitudinal matched-group design. Data were collected in a clinical setting at postoperative cochlear implant check-ups after 3, 6, 9, 12, 18, 24, 36, and 48 months of implant use. The sample included 42 children: 21 cochlear implant users and 21 with normal hearing, matched pairwise according to gender and chronological age. Communication assessments included the LittlEARS questionnaire, the Mullen Scale of Early Learning, and the Minnesota Child Development Inventory.

Results

The cochlear implant users’ hearing function according to LittlEARS was comparable to that of normal-hearing children within 9 months post-implantation. The mean scores after 9 and 12 months were 31 and 33, respectively in the prelingually deaf versus 31 and 34 in the normal-hearing children. The children's receptive and expressive language scores showed that after 12-48 months with cochlear implants, 81% had receptive language skills within the normative range and 57% had expressive language skills within the normative range. The number of children who scored within the normal range increased with increasing CI experience.

Conclusions

The present study showed that prelingually deaf children's ability to develop complex expressive and receptive spoken language after early bilateral implantation appears promising.The majority of the children developed language skills at a faster pace than their hearing ages would suggest and over time achieved expressive and receptive language skills within the normative range.     

Sound localization ability of young children with bilateral cochlear implants.

OBJECTIVE: To evaluate the benefit of bilateral cochlear implantation in young children. STUDY DESIGN: Clinical trial comparing a group of bilaterally implanted children with a group of unilaterally implanted children. SETTING: Tertiary referral center. PATIENTS: Five bilaterally implanted children (mean age at testing, 3 yr 7 mo) were compared with 5 unilaterally implanted children (mean age at testing, 5 yr 3 mo). Meningitis was the cause of deafness in all of the children. METHODS: Children were asked to localize a prerecorded melody band limited from 500 to 4,000 Hz presented from loudspeakers placed at either -90 or 90 degrees or -30 or 30 degrees azimuth. Their parents filled in the Speech, Spatial and Qualities of Hearing Scale (SSQ) and PedsQL questionnaires on hearing and health-related quality of life of their children. RESULTS: The bilaterally implanted children had significantly better scores on the localization test than the children with unilateral cochlear implants. The scores of the children with bilateral cochlear implants were also significantly higher on the spatial domain of the SSQ, which concerns localization. No significant differences were found in the speech and quality of hearing domains and the total scores on the SSQ or the PedsQL between the two groups. CONCLUSION: Children with bilateral cochlear implantation already demonstrate an advantage over unilaterally implanted children at a young age.     

Comparison of bilateral and unilateral cochlear implants in children with sequential surgery

Objective

The objective of this study was to evaluate the effect of bilateral versus unilateral cochlear implants and the importance of the inter-implant interval.

Methods

Seventy-three prelingually deaf children received sequential bilateral cochlear implants. Speech recognition in quiet with the first, second and with both implants simultaneously was evaluated at the time of the second implantation and after 12 and 24 months.

Results

Mean bilateral speech recognition 12 and 24 months after the second implantation was significantly higher than that obtained with either the first or the second implant. The addition of a second implant was demonstrated to have a beneficial effect after both 12 and 24 months. Speech recognition with the second implant increased significantly during the first year. A small, non-significant improvement was observed during the second year. The inter-implant interval significantly influenced speech recognition with the second cochlear implant both at 12 and 24 months, and bilateral speech recognition at 12 months, but not at 24 months.

Conclusions

A small, but statistically significant improvement in speech recognition was found with bilateral cochlear implants compared with a unilateral implant. A major increase in speech recognition occurred with the second cochlear implant during the first year. A shorter time interval between the two implantations resulted in better speech recognition with the second implant. However, no definitive time-point was found for when the second implant could no longer add a positive effect.     

Effects of bilateral cochlear implants in children: Timing of second surgery and the significance of wearing bilateral cochlear implants in Japan

ObjectiveThis study aims to evaluate the speech perception with first, second, or bilateral cochlear implants (CI) and to reveal the effects of wearing bilateral CI in children.MethodsAfter reviewing the medical records, a total of 19 children who underwent bilateral cochlear implantation serially between 2012 and 2015 at Kyoto University Hospital (tertiary referral center) were included in this study. All patients had no delay in language development. The study group comprised nine boys and ten girls, and their age ranged from 3 years 8 months to 12 years 5 months when they underwent the tests in this study. The mean and median ages were 8 years 6 months and 9 years 2 months, respectively.We measured the appropriate signal/noise ratio (SNR) to test speech perception of Japanese language in noise by testing the hearing ability of unilateral CI patients with or without noise and by surveying the sound environment in a classroom of a mainstream elementary school.Speech perception in quiet and noise and the left-right localization ability were examined using first, second, or bilateral cochlear implants in all patients.ResultsConsidering the results of hearing ability tests with noise and the SNR of the elementary school classrooms, we decided to use SNR of +10 dB to evaluate the speech perception ability in noise. The speech perception ability using the second CI was significantly worse in patients undergoing second cochlear implantation after 7 years old than in those who underwent surgery before 3.5 years old. Moreover, patients undergoing second cochlear implantation before 7 years old showed significantly better left–right localization of high-frequency sound.ConclusionsSecond cochlear implantation before 7 years old is a critical factor in acquiring beneficial speech perception ability with the second CI and sound localization ability with the bilateral CI.     

Developmental constraints on language development in children with cochlear implants

Research on pediatric cochlear implantation has frequently shown that speech perception, speech production, and language outcomes are better for children who are implanted earlier in life than later. These findings are often explained on the grounds that earlier implantation takes advantage of a critical or sensitive period. This paper reviews the literature concerning sensitive periods within the framework of speech and language development. It particularly emphasizes two alternate mechanisms proposed for these periods: an experience-independent mechanism, and an experience-dependent mechanism. Based on this literature review we proposed that research in the field of pediatric cochlear implantation needs to carefully define what kind of evidence is needed to reflect a sensitive period for speech and language learning. The field also needs to consider designing studies that allow the viability of these two mechanisms to be tested. An example of such a study is provided within.     

Developmental constraints on language development in children with cochlear implants

Research on pediatric cochlear implantation has frequently shown that speech perception, speech production, and language outcomes are better for children who are implanted earlier in life than later. These findings are often explained on the grounds that earlier implantation takes advantage of a critical or sensitive period. This paper reviews the literature concerning sensitive periods within the framework of speech and language development. It particularly emphasizes two alternate mechanisms proposed for these periods: an experience-independent mechanism, and an experience-dependent mechanism. Based on this literature review we proposed that research in the field of pediatric cochlear implantation needs to carefully define what kind of evidence is needed to reflect a sensitive period for speech and language learning. The field also needs to consider designing studies that allow the viability of these two mechanisms to be tested. An example of such a study is provided within.