Graeme Clark Collection
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ItemPotential and limitations of cochlear implants in children( 1995)Multiple-channel cochlear implants have been in use with children and adolescents for 8 years. The speech perception, speech production, and language of many of these children has been investigated in some detail.l-4 There have been many predictions about factors that may affect the performance of children with implants. For instance, it has been suggested that children with a congenital loss of hearing would not have the same potential to benefit from a cochlear implant as those with an acquired loss. Similarly, it has been suggested that younger children are likely to gain more benefit from a cochlear implant because of the effect of various critical ages for language learning.5 As more results have become available, it has been our observation that the performance of any particular child with a cochlear implant does not appear to follow well-defined rules, and that generalizations about the potential of certain groups of children are likely to encounter many exceptions. We now have a large quantity of results for children using cochlear implants, and it may be possible to determine some of the factors that have a significant effect on performance. This paper will attempt to identify some of these factors by reviewing speech perception results for 100 children implanted with the Nucleus 22-channel cochlear prosthesis in Australia and speech perception results for adult patients. This analysis will use an "information processing" model of a child using a cochlear implant. That is, we will assume that a child will benefit from a cochlear implant in terms of speech perception, production, and language development, if he or she receives a maximal amount of auditory information from the environment, and is able to process this information successfully. This model divides potential limiting or predictive factors into those that affect the information presented to the auditory system (eg, implant technology, surviving auditory neurons) and those that affect the processing of this information (eg, development of central auditory pathways, amount and consistency of auditory input).
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ItemVowel imitation task: results over time for 28 cochlear implant children under the age of eight years( 1995)With increasing numbers of implanted children under the age of 4 years, numerous researchers have reminded us of the need for valid, sensitive, and reliable tests of developing speech perception.1,2 In addition to studies of the efficacy of implanted prostheses, there is a need to investigate the many variables that influence children's communicative performance, such as changes in speech-coding strategy, updated speech-processing systems, the effects of various training regimens, and the selection of educational and communication modes.
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ItemSpeech perception, production and language results in a group of children using the 22-electrode cochlear implant( 1992)Five children out of a group of nine (aged 5.5 to 19.9 years) implanted with the 22-electrode cochlear implant (Cochlear Ply. Ltd.) have achieved substantial scores on open-set speech tests using hearing without lipreading. Phoneme scores for monosyllabic words ranged from 40% to 72%. Word scores in sentences ranged from 26% to 74%. Four of these five children were implanted during preadolescence. The fifth child, who had a progressive loss and was implanted during adolescence after a short period of very profound deafness, scored highest on all speech perception tests. The remaining four children who did not demonstrate open-set recognition were implanted during adolescence after a long duration of profound deafness. Post-operative performance on closed-set speech perception tests was better than pre-operative performance for all children. Improvements in speech and language assessments were also noted. These improvements tended to be greater for the younger children. The results are discussed with reference to variables which may contribute to successful implant use: such as age at onset, duration of profound hearing loss, age at implantation, aetiology, educational program, and the type of training provided.
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ItemEducational assessment and management of children with multichannel cochlear implants( 1987)This paper describes the assessment and training program to evaluate speech, language, and communication skills of profoundly deaf children during and after training. Two sensory aids/prostheses are used: hearing aids and the Nucleus multichannel cochlear implant. Using a single-subject time-series experimental design, children's speech, language, and communication skills are assessed. For speech skills, assessment includes formal tests of articulation and intelligibility, syllable stress and process analyses, analyses of suprasegmental features, and voice quality. For general communication abilities, conversational skills with different speakers, story production skills, comprehension and expression of procedural information, discourse skills, and a measure of conversational interaction skills (pragmatics) are analyzed at regular intervals. Regular observations also sample the subjects' mode and frequency of interactions with individuals and groups in the school and home setting. Normative tests and formal analyses of language samples are also used to assess the overall language age of the child, vocabulary size, and kinds of expressive and receptive, syntactic, and semantic ability.
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ItemPreliminary results for the Cochlear Corporation multielectrode intracochlear implant in six prelingually deaf patients( 1987)The preliminary results from this study indicate that some prelingually deaf patients may get worthwhile help from a multiple-electrode cochlear implant that uses a formant-based speech processing strategy. It is encouraging that these improvements can occur in young adults and teenagers. The results for two children are also encouraging. A 10-year-old child obtained significant improvement on some speech perception tests. It was easy to set thresholds and comfortable listening levels on a 5-year-old child, and he is now a regular user of the device. There are, however, considerable variations in performance among the prelingual patients, which may be related to the following factors: whether they have had some hearing after birth, the method of education used, the motivation of the patient, and age at implantation.
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ItemRehabilitation strategies for adult cochlear implant users(Monduzzi Editore, 1997)This paper summarizes open-set speech perception results using audition alone for a large group of adult Nucleus cochlear implant users in Melbourne. The results show wide variation in performance but significant improvement over the years from 1982 to 1995. Analysis of these results shows that speech processor developments have made the major contribution to this improvement over this time. Recent results for patients using the SPECTRA-SPEAK processor show !hat most subjects obtain good speech perception within six months of implantation and the need for intensive auditory training is minimal for many of these patients. Postoperative care should encourage consistent device use by providing opportunities for success and providing long term technical support for implant users. In some cases, including elderly patients, those with long term profound deafness, and those with special needs, there will still be a need for additional rehabilitation and auditory training support.
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ItemFactors affecting outcomes in children with cochlear implants(Monduzzi Editore, 1997)Open-set speech perception tests were completed for a group of 52 children and adolescents who were long-term users of the Nucleus multiple channel cochlear prosthesis. Results showed mean scores for the group of 32.4% for open-set BKE sentences and 48.1% for phonemes in open-set monosyllabic words. Over 80% of the group performed significantly on these tas1cs. Age at implantation was identified as a significant factor affecting speech perception performance with improved scores for children implanted early. This factor was evident in the results at least down to the age of three years. Duration.. of profound hearing loss, progressive hearing loss, educational program and preoperative residual hearing were also identified as significant factors that may affect speech perception performance.
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ItemThe auditory cortex and auditory deprivation: experience with cochlear implants in the congenitally deaf [Abstract]( 1995)The primary auditory cortex (AI) exhibits a topographic representation of the organ of Corti in normal hearing animals. Plasticity studies have shown that this orderly representation of frequency can be modified following a restricted hearing loss or by behavioural trainingl,2. Little is known, however, of the effects of a profound hearing loss on AI, although a number of early studies have suggested an enhancement of activity from other modalities3. Knowledge of the functional status of the central auditory pathway in the profoundly deaf, and the ability of these structures to undergo reorganization particularly following long periods of auditory deprivation - are important issues for the clinical management of cochlear implant patients. In this paper we review our recent clinical and experimental experience with cochlear implants in the congenitally deaf.
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ItemHabilitation issues in the management of children using the cochlear multiple-channel cochlear prosthesis( 1993)Since 1985, a significant proportion of patients seen In the Melbourne cochlear Implant clinic have been children. The children represent a diverse population, with both congenital and acquired hearing-impairment, a wide-range or hearing levels pre-Implant, and an age range from 2 years to 18 years. The habilitation programme developed for the overall group must be flexible enough to be tailored to the Individual needs of each child, and to adapt to the changing needs or children as they progress. Long-term data shows that children are continuing to show Improvements after 5-7 years of device use, particularly In their perception of open-set words and sentences. Habilitation programs must therefore be geared to the long-term needs of children and their families. Both speech perception and speech production need to be addressed In the specific content of the habilitation program for any Individual child. In addition, for young children, the benefits or Improved speech perception should have an Impact on development of speech and language, and the focus of the programme for this age child will reflect this difference In emphasis. Specific materials and approaches will vary for very young children, school-age and teenage children. In addition, educational selling will have a bearing on the Integration of listening and device use Into the classroom environment.
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ItemFuture developments in speech processing for multichannel cochlear implants in children [Abstract]( 1992)The average speech perception score for adult implant patients is now about 60% on an open-set sentence test without lipreading. This is higher than the scores obtained by many profound and severe-to-profoundly impaired hearing aid users. This suggests that some hearing aid users, particularly those who use a hearing aid in one ear only, could benefit from a cochlear implant. As neither the implant nor the hearing aid will provide perfect speech recognition it is to be expected that this group should obtain maximum benefit by using the hearing aid in one ear together with the implant in the other ear. However, experience with this group of patients has shown that many people find the use of two independent devices unacceptable. Furthermore, perceptual interaction of the acoustic and electrical signals makes it desirable to be able to control the two outputs in a more co-ordinated way than is possible with two independent devices. Consequently, a "bimodal" speech processor has been developed with both acoustic and electrical outputs controlled from the same speech processing unit. Feature coding aspects of the implant processing have been applied to the acoustic signal in such a way as to enhance speech perception with the hearing aid and improve compatibility with the implant. Initial testing with the bimodal aid shows promise to help severely-to-profoundly impaired individuals. The device has also been useful as a research tool to investigate the complex interactions of simultaneous acoustic and electrical stimulation. The Spectral Maxima Sound Processor (SMSP) has also been developed at the University of Melbourne for use with the Nucleus cochlear implant. Studies with adult subjects have shown improved perception of vowels, consonants, words and sentences in quiet and sentences in background noise with the SMSP as compared with the MSP(MULTIPEAK) which is currently supplied for use with this implant. Results for four subjects showed mean scores for open set sentences at a 10 dB signal-to-noise ratio of 78.7% for the SMSP and 50.0% for the MSP. Mean scores for the same group on open set monosyllabic words in quiet were 57.4% for SMSP and 39.9% for MSP. These results suggest that future improvements in speech perception will be possible for children using the Nucleus cochlear implant.