Graeme Clark Collection

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    Speech perception in implanted children: influence of preoperative residual hearing on outcomes [Abstract]
    Cowan, R. S. C. ; Barker, E. J. ; Pegg, P. ; Dettman, S. ; Rennie, M. ; Galvin, K. ; Meskin, T. ; Rance, G. ; Cody, K. ; Sarant, J. ; Larratt, M. ; Latus, K. ; HOLLOW, RODNEY ; Rehn, C. ; Dowell, R. C. ; Pyman, B. ; Gibson, W. P. R. ; Clark, Graeme M. ( 1998)
    Since the first child was implanted with the Nucleus 22-channel prosthesis in Melbourne in 1985, several thousand children world-wide have now benefitted from this technology. More effective paediatric assessment and management procedures have now been developed, allowing cochlear implants to be offered to children under the age of 2 years. Improvements in speech processing strategy have also been implemented in the Nucleus implant system, resulting in increased mean speech perception benefits for implanted adults. Although a range of performance on formal measures of hearing, speech or language has been reported for children using implants, results from the first decade of implant experience consistently show that significant benefits are available to children receiving their implant at an early age. Reported speech perception results for implanted children show that a considerable proportion (60%) of paediatric patients in the Melbourne and Sydney clinics are able to understand some open-set speech using electrical stimulation alone. These results, and the upward trend of mean speech perception benefits shown for postlinguistically deafened adults have raised questions as to whether severely, or severely-to-profoundly deaf children currently using hearing aids would in fact benefit more from a cochlear implant. To investigate the potential influence of the degree of preoperative residual hearing on postoperative speech perception, results for all implanted children in the Melbourne and Sydney cochlear implant programs were analysed. Results showed that as a group, children with higher levels of preoperative residual hearing were consistently more likely to achieve open-set speech perception benefits. Potential factors in this finding could be higher levels of ganglion cell survival or greater patterning of the auditory pathways using conventional hearing aids prior to implantation. Conversely, children with the least preoperative residual hearing were less predictable, with some children achieving open-set perception, and others showing more limited closed-set benefits to perception. For these children, it is likely that preoperative residual hearing is of less significance than other factors in outcomes.
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    The progress of children using the multichannel cochlear implant in Melbourne
    Cowan, R. S. C. ; Dowell, R. C. ; Hollow, R. ; Dettman, S. J. ; Rance, G. ; Barker, E. J. ; Sarant, J. Z. ; Galvin, K. L. ; Webb, R. C. ; Pyman, B. C. ; Cousins, V. C. ; Clark, Graeme M. ( 1995)
    Multi-channel cochlear implantation in children began in Australia in 1985 and there are now close to 4000 profoundly deaf children and adolescents using the Australian implant system around the world. The aim of the implant procedure is to provide adequate hearing for speech and language development through auditory input. This contrasts with the situation for adults with acquired deafness where the cochlear implant aims to restore hearing for someone with well-developed auditory processing and language skills. As with adults, results vary over a wide range for children using the Multi-channel implant. Many factors have been suggested that may contribute to differences in speech perception for implanted children. In an attempt to better understand these factors, the speech perception results for children implanted in Melbourne were reviewed and subjected to statistical analysis. This has indicated that the amount of experience with the implant and the length of sensory deprivation are strongly correlated with perceptual results. This means that younger children are likely to perform better with an implant and that a number of years of experience are required for children to reach their full potential. The results have also indicated that educational placement and management play a crucial role in children reaching their potential. Overall, 60% of the children and adolescents in the study have reached a level of open-set speech understanding using the cochlear implant without lipreading.
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    Comparison of the SPEAK (Spectral Maxima) and multipeak speech processing strategies and improved speech perception in background noise
    Clark, Graeme M. ; Whitford, L. ; Van Hoesel, R. ; McKay, C. M. ; McDermott, H. D. ; Seligman, P. ; Vandali, A. ; Pyman, B. C. ; Cowan, R. C. ( 1995)
    As more is known about speech processing for Cochlear Implant patients, results should continue to improve. It now appears possible that Cochlear Implant patients may, in some instances, reach performance levels that are better than those obtained by most severely deaf people who use hearing aids.
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    Vowel imitation task: results over time for 28 cochlear implant children under the age of eight years
    Dettman, S. J. ; Barker, E. J. ; Dowell, R. C. ; Dawson, P. W. ; Blamey, P. J. ; Clark, Graeme M. ( 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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    Preoperative residual hearing as a predictor of postoperative speech scores for adult cochlear implant users [Abstract]
    COWAN, ROBERT ; HOLLOW, RODNEY ; DOWELL, RICHARD ; PYMAN, BRIAN ; Clark, Graeme M. ( 1994)
    The development of multiple channel cochlear implants has been a significant advance in the rehabilitation of profound hearing loss. Speech perception benefits have been particularly evident for postlinguistically deafened adults, who as a group have shown not only supplementation of lipreading scores but also significant comprehension of words and sentences using an implant alone, without the aid of lipreading. In many cases, patients are able to use their implant for telephone conversation. Speech perception benefits for adult users have increased with advances in speech processing and improved means of habilitation. These improvements in open-set speech benefits for adult users have resulted in a steady increase in group mean scores and a reevaluation of selection criteria for cochlear implantation. In the initial development of cochlear implants, only those with little or no residual hearing were considered as candidates. Current selection criteria now include those with substantial residual hearing, who may score up to 40% in the best-aided condition on word and sentence speech perception tests. In order to provide realistic expectations for prospective cochlear implant patients, it is important to establish the relationship of many preimplant factors to postimplant speech perception benefits. For severely hearing impaired adults, the relationship between preoperative residual hearing, as measured by aided word and sentence speech perception test scores, and postoperative speech perception benefits is of significant interest. Analysis of data collected over a 15 year period for adult patients is presented. The rationale for conducting full speech perception assessments for all potential cochlear implant patients is stressed.
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    The evolution continues: the clinical trials of the SPEAK strategy in Nucleus 22 channel cochlear implant users [Abstract]
    Antognelli, Trisha ; Whitford, Lesley ; SELIGMAN, PETER ; Everingham, Colleen ; Skok, Marisa ; Plant, Kerrie ; Hollow, Rod ; Staller, Steve ( 1994)
    Research in the field of cochlear implants continues in centres around the world. The aim of all centres is to improve the speech perception abilities of those children and adults fitted with a cochlear implant. Most recently the work of Hugh McDermott and Colette McKay (Melbourne University, Department of Otolaryngology) in developing and researching the SMSP (Spectral Maxima Sound Processor) has greatly enhanced the speech understanding abilities of a number of subjects implanted with the Nucleus 22 Channel Cochlear Implant.
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    A new portable sound processor for the University of Melbourne/ Nucleus Limited multielectrode cochlear implant
    McDermott, Hugh J. ; McKay, Colette M. ; Vandali, Andrew E. ( 1992)
    Abstract not available due to copyright.
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    Cochlear implants in children, adolescents, and prelinguistically deafened adults: speech perception
    Dawson, Pam W. ; Blamey, Peter J. ; Rowland, Louise C. ; Dettman, Shani J. ; Clark, Graeme M. ; Busby, Peter A. ; Brown, Alison M. ; Dowell, Richard C. ; Rickards, Field W. ( 1992)
    A group of 10 children, adolescents, and prelinguistically deafened adults were implanted with the 22-electrode cochlear implant (Cochlear Ply Ltd) at the University of Melbourne Cochlear Implant Clinic and have used the prosthesis for periods from 12 to 65 months. Postoperative performance on the majority of closed-set speech perception tests was significantly greater than chance, and significantly better than preoperative performance for all of the patients. Five of the children have achieved substantial scores on open-set speech tests using hearing without lipreading. Phoneme scores in monosyllabic words ranged from 30% to 72%; word scores in sentences ranged from 26% to 74%. Four of these 5 children were implanted during preadolescence (aged 5:5 to 10:2 years) and the fifth, who had a progressive loss, was implanted during adolescence (aged 14:8 years). The duration of profound deafness before implantation varied from 2 to 8 years. Improvements were also noted over postoperative data collection times for the younger children. The remaining 5 patients who did not demonstrate open-set recognition were implanted after a longer duration of profound deafness (aged 13:11to 20:1 years). The results are discussed with reference to variables that may affect implant performance, such as age at onset of loss, duration of profound loss, age at implantation, and duration of implantation. They are compared with results for similar groups of children using hearing aids and cochlear implants.
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    Preliminary speech perception results for children with the 22-electrode Melbourne/ cochlear hearing prosthesis
    Cowan, R. S. C. ; Dowell, R. C. ; Pyman, B. C. ; Dettman, S. J. ; Dawson, P. W. ; Rance, G. ; Barker, E. J. ; Sarant, J. Z. ; Clark, Graeme M. ( 1993)
    The 22-electroce cochlear prosthesis developed by the University of Melbourne and Cochlear Pty. Ltd. has been shown to provide significant speech perception benefits to profoundly deafened adults. More recently, use of an improved Multipeak encoding strategy has significantly improved speech perception performance both in quiet and in noise. Benefits to speech perception in children have not as yet been fully documented, in part due to the shorter history of implant use in children and the smaller overall number of children implanted as compared with adults. The first implantation of the 22-electrode cochlear prosthesis in a child was carried out in Melbourne in January of 1985. In Melbourne, a 5-year-old child was operated on in April 1986, and a first congenitally deaf child in April 1987. The age of implantation has been progressively reduced, with the first 2-year-old child implanted in Melbourne in 1990. As at January 1992, approximately 1,200 children (under 18 years of age inclusive) have been implanted worldwide with the 22-electrode cochlear prosthesis. Of this number, approximately 50% are under the age of 6 years. The age of the child, aetiology of the hearing loss, age at onset and duration of the hearing loss, education program attended both prior to and subsequent to implantation, and parental motivation to assist in habilitation are all factors which may affect an individual child's development and progress with the device. Evaluation of performance in children is complicated by a number of issues, including the effects of delayed speech and language development, and the ability of individual children to perform auditory tests. The measure of performance chosen for any evaluation will also reflect the interests of the particular clinician. For example, effects of device use on speech production may be of interest to the speech therapist, whereas educational progress will be of primary importance to the teacher of an implanted child. However, in choosing an appropriate evaluation test to measure progress woth the cochlear prosthesis, it is vital to realize that all measures such as effects of device use on speech production, educational progress, development of language, and effects on social and communication skills depend on the child being able to accurately perceive speech information through her/his device.
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    The clinical trial of a multi-channel cochlear prosthesis
    Pyman, B. C. ; Clark, Graeme M. ; Dowell, R. C. ; Webb, R. L. ; Brown, A. M. ; Bailey, Q. E. ; Luscombe, S. M. ( 1983)
    The results of a multiple-electrode cochlear implant carried out on 1st August, 1978 on a totally deaf patient (post-lingual hearing loss) showed that he could perceive sounds of different pitches depending on the electrode stimulated, and this finding was consistent with the place theory of frequency coding. Furthermore, stimulating individual electrodes produced percepts which the patient described as vowel-like in quality. The patient could also perceive different pitches which varied with the rate of stimulation up to 200 pulses/second, but at higher rates he had difficulties perceiving pitch changes (Clark et al. 1978; Tong et al, 1979). As a result of the psychophysical studies a speech processor was developed. The speech processor extracted: firstly, the voicing frequency to help the patient hear the rhythm of speech and know whether a speech sound was voiced or unvoiced (e.g., /b/ versus /p/); and, secondly, the second formant to enable the patient to recognize vowels and consonants and so hear words. In order to maximize speech intelligibility, the second formant stimulated an appropriate electrode, and the rate of stimulation on that electrode was related to the voicing frequency.