Graeme Clark Collection
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ItemThe progress of children using the multichannel cochlear implant in Melbourne( 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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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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ItemCochlear implants in children, adolescents, and prelinguistically deafened adults: speech perception( 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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ItemMultichannel cochlear implantation in children: a summary of current work at The University of Melbourne( 1991)This paper summarizes research work relating to multichannel cochlear implantation in children at the University of Melbourne. Ongoing safety studies relating to the implantation of young children are discussed. Results of these studies suggest that special design considerations are necessary for a prosthesis to be implanted in children under the age of 2 years. Results of clinical assessment of implanted children and adolescents are also discussed in terms of speech perception, speech production, and language development, and some possible predictive factors are suggested. Preliminary data suggests that a high proportion of young children can achieve open-set speech perception with the cochlear implant given appropriate training and support. Initial results with adults using new speech processing hardware and a new coding scheme are also presented. These suggest that improved speech perception in quiet and competing noise is possible with the new system.
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ItemThe histopathology of the human temporal bone and auditory central nervous system following cochlear implantation in a patient: correlation with psychophysics and speech perception results( 1988)Cochlear implantation has become a recognised surgical procedure for the management of a profound-total hearing loss, especially in patients who have previously had hearing before going deaf (postlingual deafness). Nevertheless, it is important for progress in the field that patients who have had a cochlear implant, bequeath their temporal bones for research. This will then make it possible to further assess the safety of the procedure, and the factors that are important for its effectiveness. Biological safety has been assessed in a number of studies on animals, in particular, the biocompatibility of the materials used (1,2), the histopathological effects of long-term implantation on the cochlea (3, 4, 5, 6, 7, 8), and the effects of chronic electrical stimulation on the viability of spiral ganglion cells (9, 10, 11, 12). In studying the temporal bones of deceased cochlear implant patients it is possible to help establish that the animal experimental results are applicable to Man. Surgical trauma has been most frequently evaluated by inserting electrodes into cadaver temporal bones. It is important, however, to examine bones that have been previously implanted surgically to ensure that the cadaver findings are applicable to operations on patients. The effectiveness of cochlear implantation can be studied by correlating the histopathological findings, the dendrite and spiral ganglion cell densities, in particular, with the psychophysical and speech perception results. Other benefits also accrue, for example, establishing the accuracy of preoperative X-rays and electrical stimulation of the promontory in predicting cochlear pathology and spiral ganglion cell numbers. For the above reasons it has been especially interesting to examine both the temporal bones and central nervous system from one of our patients (patient 13) who participated in the initial clinical trial of the Cochlear Proprietary Limited (a member of the Nucleus group) multiple-electrode cochlear prosthesis, and who died due to a myocardial infarction following coronary bypass surgery.
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ItemThe clinical trial of a multi-channel cochlear prosthesis( 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.
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ItemPreoperative hearing aid evaluations for cochlear implant patients: a preliminary report using a minimal auditory capabilities battery( 1983)Two profoundly deaf patients were evaluated using the Minimal Auditory Capabilities (MAC) battery of speech discrimination tests. One patient was a multiple-channel cochlear implant patient (MC1) using a wearable speech-processor, the other a prospective cochlear implant patient using a hearing aid (HA). Results from the MAC battery showed that MC1 received significantly more auditory information via the speech-processor than was provided by the hearing aid to HA. These results indicated that the cochlear implant could be a suitable alternative for HA. However, the results indicated that HA gained some minimal benefit from the hearing aid and these results should be taken into consideration when deciding which ear should be implanted.
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ItemClinical trial of a multiple-channel cochlear prosthesis: an initial study in four patients with profound total hearing loss( 1983)The clinical trial of a multiple-channel cochlear prosthesis was undertaken in four patients with postlingual deafness and profound total hearing loss. The results of open-set speech tests confirmed that, using electrical stimulation alone, one patient could have a meaningful conversation with resorting to lipreading (for example, this patient uses the prosthesis to converse with her husband on the telephone). The results of closed-set speech tests also suggested that a multiple-channel stimulator is more effective than a single-channel one in conveying speech information. The cochlear prosthesis was especially effective in all four patients when it was used in conjunction with lipreading, and speech-tracking tests showed that the patients could combine the information obtained from both electrical stimulation and lipreading.
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ItemA multiple-channel cochlear implant and wearable speech-processor: an audiological evaluation( 1981)Standard audiological tests were administered to a totally deft multiple-channel cochlear implant patient with a wearable speech-processor in a monitored sound field under the following conditions: a wearable unit activated alone (WA), lipreading with the wearable unit off (LA), and wearable unit activated in combination with lipreading (WL). Thresholds obtained for narrow-band noise signals indicated that the wearable unit allowed the patient to detect a variety of sounds at different frequencies. The results obtained in closed-set word tests and open-set word and sentence tests showed significant improvements in word and sentence scores from LA to WL. In the open-se (C.I.D) sentence tests, the patient scored 22% for LA and 76% for WL. The WL score of 76% correlates with a satisfactory performance in understanding connected speech. The patient also scored 30% correct in a test involving the recognition of environmental sounds.