Development of visual attention skills in prelingually deaf children who use cochlear implants.

OBJECTIVE: To determine the effects of length of cochlear implant use and other demographic factors on the development of sustained visual attention in prelingually deaf children and to examine the relations between performance on a test of sustained visual attention and audiological outcome measures in this population. DESIGN: A retrospective analysis of data collected before cochlear implantation and over several years after implantation. Two groups of prelingually deaf children, one >6 years old (N = 41) and one <6 years old (N = 47) at testing, were given an age-appropriate Continuous Performance Task (CPT). In both groups, children monitored visually presented numbers for several minutes and responded whenever a designated number appeared. Hit rate, false alarm rate, and signal detection parameters were dependent measures of sustained visual attention. We tested for effects of a number of patient variables on CPT performance. Multiple regression analyses were conducted to determine if CPT scores were related to performance on several audiological outcome measures. RESULTS: In both groups of children, mean CPT performance was low compared with published norms for normal-hearing children, and performance improved as a function of length of cochlear implant use and chronological age. The improvement in performance was manifested as an increase in hit rate and perceptual sensitivity over time. In the younger age group, a greater number of active electrodes predicted better CPT performance. Results from regression analyses indicated a relationship between CPT response criterion and receptive language in the younger age group. However, we failed to uncover any other relations between CPT performance and speech and language outcome measures. CONCLUSIONS: Our findings suggest that cochlear implantation in prelingually deaf children leads to improved performance on a test of sustained visual processing of numbers over 2 or more years of cochlear implant use. In preschool-age children who use cochlear implants, individuals who are more conservative responders on the CPT show higher receptive language scores than do individuals with more impulsive response patterns. Theoretical accounts of these findings are discussed, including cross-modal reorganization of visual attention and enhanced phonological encoding of visually presented numbers.

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.

Positron emission tomography in cochlear implant and auditory brainstem implant recipients.

UNLABELLED: Positron emission tomography (PET) imaging was used to evaluate the brain's response to auditory stimulation, including speech. Five cases of adults illustrate the utility of PET to illuminate auditory processing with cochlear or brainstem implants. Subjects showed varying degrees of success in processing speech, which was reflected in the resulting PET images. Functional speech processing was associated with activation in areas classically associated with speech processing. In one patient who did not achieve functional speech processing, activation in frontal regions suggests that the subject used other cognitive strategies to assist auditory processing. LEARNING OUTCOMES: As a result of this activity, the participant will be introduced to the principles of PET and the application of this technology to deaf patients who have received an implanted auditory prosthesis.

Cochlear implants in children.

Cochlear implants are electronic prostheses that provide a high quality sense of hearing to severely and profoundly deaf children and adults. As improvements in surgical technique and device performance have occurred, indications for implantation have expanded.

Language development in profoundly deaf children with cochlear implants.

Although cochlear implants improve the ability of profoundly deaf children to understand speech, critics claim that the published literature does not document even a single case of a child who has developed a linguistic system based on input from an implant. Thus, it is of clinical and scientific importance to determine whether cochlear implants facilitate the development of English language skills. The English language skills of prelingually deaf children with cochlear implants were measured before and after implantation. We found that the rate of language development after implantation exceeded that expected from unimplanted deaf children (p < .001) and was similar to that of children with normal hearing. Despite a large amount of individual variability, the best performers in the implanted group seem to be developing an oral linguistic system based largely on auditory input obtained from a cochlear implant.

Speech perception in children with cochlear implants: effects of lexical difficulty, talker variability, and word length.

The present results demonstrated that all 3 factors --lexical difficulty, stimulus variability, and word length--significantly influenced spoken word recognition by children with multichannel cochlear implants. Lexically easy words were recognized significantly better than lexically hard words, regardless of talker condition or word length of the stimuli. These results support the earlier findings of Kirk et al(12) obtained with live-voice stimulus presentation and suggest that lexical effects are very robust. Despite the fact that listeners with cochlear implants receive a degraded speech signal, it appears that they organize and access words from memory relationally in the context of other words. The present results concerning talker variability contradict those previously reported in the literature for listeners with normal hearing(7,11) and for listeners with mild-to-moderate hearing loss who use hearing aids.(14) The previous investigators used talkers and word lists different from those used in the current study and found that word recognition declined as talker variability increased. In the current study, word recognition was better in the multiple-talker condition than in the single-talker condition. Kirk(15) reported similar results for postlingually deafened adults with cochlear implants who were tested on the recorded word lists used in the present study. Although the talkers were equally intelligible to listeners with normal hearing in the pilot study, they were not equally intelligible to children or adults with cochlear implants. It appears that either the man in the single-talker condition was particularly difficult to understand or that some of the talkers in the multiple-talker condition were particularly easy to understand. Despite the unexpected direction of the talker effects, the present results demonstrate that children with cochlear implants are sensitive to differences among talkers and that talker characteristics influence their spoken word recognition. We are conducting a study to assess the intelligibility of each of the 6 talkers to listeners with cochlear implants. Such studies should aid the development of equivalent testing conditions for listeners with cochlear implants. There are 2 possible reasons the children in the present study identified multisyllabic words better than monosyllabic words. First, they may use the linguistic redundancy cues in multisyllabic words to aid in spoken word recognition. Second, multisyllabic words come from relatively sparse lexical neighborhoods compared with monosyllabic tokens. That is, multisyllabic words have fewer phonetically similar words, or neighbors, competing for selection than do monosyllabic stimuli. These lexical characteristics most likely contribute to the differences in identification noted as a function of word length. The significant lexical and word length effects noted here may yield important diagnostic information about spoken word recognition by children with sensory aids. For example, children who can make relatively fine phonetic distinctions should demonstrate only small differences in the recognition of lexically easy versus hard words or of monosyllabic versus multisyllabic stimuli. In contrast, children who process speech using broad phonetic categories should show much larger differences. That is, they may not be able to accurately encode words in general or lexically hard words specifically. Further study is warranted to determine the interaction between spoken word recognition and individual word encoding strategies.

Positron emission tomography in cochlear implant and auditory brain stem implant recipients.

OBJECTIVE: The purpose of this study was to determine whether similar cortical regions are activated by speech signals in profoundly deaf patients who have received a multichannel cochlear implant (CI) or auditory brain stem implant (ABI) as in normal-hearing subjects. STUDY DESIGN: Positron emission tomography (PET) studies were performed using a variety of discrete stimulus conditions. Images obtained were superimposed on standard anatomic magnetic resonance imaging (MRI) for the CI subjects. The PET images were superimposed on the ABI subject's own MRI. SETTING: Academic, tertiary referral center. PATIENTS: Five subjects who have received a multichannel CI and one who had received an ABI. INTERVENTION: Multichannel CI and ABI. MAIN OUTCOME MEASURE: PET images. RESULTS: Similar cortical regions are activated by speech stimuli in subjects who have received an auditory prosthesis. CONCLUSIONS: Neuroimaging provides a new approach to the study of speech processing in CI and ABI subjects.

PET imaging of cochlear-implant and normal-hearing subjects listening to speech and nonspeech.

Functional neuroimaging with positron emission tomography (PET) was used to compare the brain activation patterns of normal-hearing (NH) with postlingually deaf, cochlear-implant (CI) subjects listening to speech and nonspeech signals. The speech stimuli were derived from test batteries for assessing speech-perception performance of hearing-impaired subjects with different sensory aids. Subjects were scanned while passively listening to monaural (right ear) stimuli in five conditions: Silent Baseline, Word, Sentence, Time-reversed Sentence, and Multitalker Babble. Both groups showed bilateral activation in superior and middle temporal gyri to speech and backward speech. However, group differences were observed in the Sentence compared to Silence condition. CI subjects showed more activated foci in right temporal regions, where lateralized mechanisms for prosodic (pitch) processing have been well established; NH subjects showed a focus in the left inferior frontal gyrus (Brodmann's area 47), where semantic processing has been implicated. Multitalker Babble activated auditory temporal regions in the CI group only. Whereas NH listeners probably habituated to this multitalker babble, the CI listeners may be using a perceptual strategy that emphasizes 'coarse' coding to perceive this stimulus globally as speechlike. The group differences provide the first neuroimaging evidence suggesting that postlingually deaf CI and NH subjects may engage differing perceptual processing strategies under certain speech conditions.

Communication skills in pediatric cochlear implant recipients.

Detailed longitudinal studies of speech perception, speech production and language acquisition have justified a significant change in the demographics of congenitally and prelingually deaf children who receive cochlear implants. A trend toward earlier cochlear implantation has been justified by improvements in measures assessing these areas. To assess the influence of age at implantation on performance, age 5 years was used as a benchmark. Thirty-one children who received a Nucleus cochlear implant and use the SPEAK speech processing strategy and two children who received a Clarion cochlear implant and use the CIS strategy served as subjects. The subjects were divided into three groups based on age at implantation. The groups comprised children implanted before the age of 3 years (n = 14), children implanted between 3 years and 3 years 11 months (n = 11) and those implanted between 4 years and 5 years 3 months (n = 8). The children were further divided according to whether they used oral or total communication. The earlier-implanted groups demonstrated statistically significant improvements on measures of speech perception. Improvements in speech intelligibility as a function of age at implant were seen but did not reach statistical significance. The results of the present study demonstrate that early implantation promotes the acquisition of speaking and listening skills.

Cochlear implantation in auditory neuropathy.

OBJECTIVE: Auditory neuropathy is a recently described clinical entity characterized by sensorineural hearing loss in which the auditory evoked potential (ABR) is absent but otoacoustic emissions are present. This suggests a central locus for the associated hearing loss. In this study the results observed in a child with auditory neuropathy who received a cochlear implant are presented and compared with those of a matched group of children who were recipients of implants. METHODS: A single-subject, repeated-measures design, evaluating closed-set and open-set word recognition abilities was used to assess the subject and a control group of matched children with implants who had also experienced a progressive sensorineural hearing loss. RESULTS: The subject demonstrated improvements in vowel recognition (82% correct) by 1 year after implantation, which were only slightly lower than the control group. Consonant recognition and open-set word recognition scores were significantly lower. CONCLUSION: Caution should be exercised when considering cochlear implantation in children with auditory neuropathy. As with conventional hearing aids, less than optimal results may be seen.

Mutations in a novel cochlear gene cause DFNA9, a human nonsyndromic deafness with vestibular dysfunction.

DFNA9 is an autosomal dominant, nonsyndromic, progressive sensorineural hearing loss with vestibular pathology. Here we report three missense mutations in human COCH (previously described as Coch5b2), a novel cochlear gene, in three unrelated kindreds with DFNA9. All three residues mutated in DFNA9 are conserved in mouse and chicken Coch, and are found in a region containing four conserved cysteines with homology to a domain in factor C, a lipopolysaccharide-binding coagulation factor in Limulus polyphemus. COCH message, found at high levels in human cochlear and vestibular organs, occurs in the chicken inner ear in the regions of the auditory and vestibular nerve fibres, the neural and abneural limbs adjacent to the cochlear sensory epithelium and the stroma of the crista ampullaris of the vestibular labyrinth. These areas correspond to human inner ear structures which show histopathological findings of acidophilic ground substance in DFNA9 patients.

The effect of auditory feedback on the control of oral-nasal balance by pediatric cochlear implant users.

OBJECTIVE: This study examined the control of oral-nasal balance by pediatric cochlear implant (CI) users, with and without auditory feedback. DESIGN: Five CI users read lists of sentences in two conditions: with their devices on and with their devices off. Their oral-nasal balance (ratio of energy radiated from the oral and nasal cavities) was measured in both conditions and compared with values obtained from children with normal hearing. RESULTS: CI users showed different patterns of abnormal oral-nasal balance with their devices off, but they generally achieved values that were closer to normal when their devices were on. CONCLUSIONS: The results suggest that children with CIs use the auditory signal provided by their device to improve their control of nasalization. It is also possible that at least part of the changes in oral-nasal balance were driven by changes in related articulatory parameters.

Improvements in speech perception by children with profound prelingual hearing loss: effects of device, communication mode, and chronological age.

The present investigation expanded on an earlier study by Miyamoto, Osberger, Todd, Robbins, Karasek, et al. (1994) who compared the speech perception skills of two groups of children with profound prelingual hearing loss. The first group had received the Nucleus multichannel cochlear implant and was tested longitudinally. The second group, who were not implanted and used conventional hearing aids, was tested at a single point in time. In the present study, speech perception scores were examined over time for both groups of children as a function of communication mode of the child. Separate linear regressions of speech perception scores as a function of age were computed to estimate the rate of improvement in speech perception abilities that might be expected due to maturation for the hearing aid users (n=58) within each communication mode. The resulting regression lines were used to compare the estimated rate of speech perception growth for each hearing aid group to the observed gains in speech perception made by the children with multichannel cochlear implants. A large number of children using cochlear implants (n=74) were tested over a long period of implant use (m=3.5 years) that ranged from zero to 8.5 years. In general, speech perception scores for the children using cochlear implants were higher than those predicted for a group of children with 101-110 dB HL of hearing loss using hearing aids, and they approached the scores predicted for a group of children with 90-100 dB HL of hearing loss using hearing aids.

The effects of processor strategy on the speech perception performance of pediatric nucleus multichannel cochlear implant users.

OBJECTIVE: The present investigation examined the speech perception skills of pediatric cochlear implant users who changed from their original speech processors and strategies to the Spectral Peak (SPEAK) strategy. DESIGN: A within-subjects design was used to compare individual subject's performance using the SPEAK strategy with that obtained with their previous speech strategy (FOF1F2 or Multipeak) in this retrospective study. The subjects demonstrated a wide range of perceptual abilities and had used a cochlear implant for varying lengths of time before converting to the SPEAK strategy. RESULTS: Nine of the 11 subjects showed significant improvement on at least one of the open-set word recognition measures, whereas two subjects showed no change on any of the open-set measures when using the SPEAK strategy. CONCLUSIONS: The present results suggest that the majority of pediatric cochlear implant users are likely to show improved speech perception performance when converting to the new SPEAK processing strategy.

Cochlear implant reimplantation.

The objective of this study was to determine whether insertion length and number of active channels remained the same after reimplantation of a cochlear implant. A retrospective case review of 170 consecutively implanted multichannedl cochlear implants was conducted. Seventeen of these devices had to be replaced. Data were analyzed for the Nucleus cochlear implant users who were reimplanted in the same ear. For most subjects, insertion length and number of channels remained unchanged, but a few subjects experienced substantial decreases. When the whole group was considered, a small but statistically significant drop was noted for both parameters. In conclusion, although reimplantation is technically possible, the first procedure provides the optimal surgical environment.