Graeme Clark Collection

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    Initial results for six patients with a multiple-channel cochlear prosthesis
    Dowell, R. C. ; Brown, A. M. ; Seligman, P. M. ; Clark, Graeme M. (Monash University Press, 1983)
    A total of eight patients have been assessed with the multi-channel cochlear prosthesis at the University of Melbourne. The first two patients were implanted with a prototype device in 1978 and 1979, and their results with various speech evaluation procedures have been reported and summarized in detail elsewhere (Clark & Tong, 1982). Briefly, these results indicated that some very significant benefit could be obtained for these patients when using the cochlear prosthesis with external speech processing, particularly when using the device in conjunction with lipreading. It was also shown that some significant understanding of speech was possible without lipreading (open-set) for both patients, although this was fairly limited.
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    Rehabilitation strategies for adult cochlear implant users
    Dowell, R. C. ; Blamey, P. J. ; Clark, Graeme M. (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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    Factors affecting outcomes in children with cochlear implants
    Dowell, R. C. ; Blamey, P. J. ; Clark, Graeme M. (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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    The effect of language knowledge on speech perception in children with impaired hearing
    Sarant, J. Z. ; Blamey, P. J. ; Clark, Graeme M. ( 1996)
    Open-set words and sentences were used to assess auditory speech perception of three hearing-impaired children aged 9 to 15 years using the Nucleus 22channel cochlear implant. Vocabulary and syntax used in the tests were assessed following the initial perception tests. Remediation was given in specific vocabulary and syntactic areas, chosen separately for each child, and the children were reassessed. Two children showed a significant post-remediation improvement in their overall scores on the syntactic test and both perception measures. The third child who was older, had the best language knowledge and the lowest auditory speech perception scores, showed no significant change on any of the measures. Language remediation in specific areas of weakness may be the quickest way to enhance speech perception for some children with impaired hearing in this age range.
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    Multicenter evaluations of speech perception in adults and children with the nucleus (cochlear) 22-channel cochlear implant
    Clark, Graeme M. ; Dowell, Richard C. ; Cowan, Robert S. ; Pyman, Brian C. ; Webb, Robert L. (Kugler, 1996)
    The Nucleus 22-channel cochlear implant has been implanted in over 10,500 patients in 79 countries. and used for more than 25 languages. It arose as a result of our early physiological, behavioral and biological research on experimental animals. The historical development of the Nucleus device has been outlined in detail by Clark. Our ongoing research has led to improvements in the way speech is processed with the 22-channel device that are now resulting in improved speech perception for profoundly totally deaf people that is, on average, better than the speech perception obtained by many deaf people with hearing aids. The multiple-channel cochlear implant was first approved by the US Food and Drug Administration (FDA) for use in postlinguistically deaf adults in 1985. It was subsequently approved for use in children in 1990. The proportion of children (18 years of age and under) to have now received it is approximately 439C (4,500 out of 10.500). In evaluating improvements in speech processing it is important to design well-controlled studies, and a number of important ones which have previously been published are summarized in this paper. In addition, speech perception results for all the Nucleus speech processing strategies have been obtained four to six months postoperatively from unselected patients presenting to the Cochlear Implant Clinic at the Royal Victorian Eye & Ear Hospital (RVEEH), Melbourne, and are presented in this paper. As results can vary greatly with different durations of experience it is essential to make comparisons at the same time postoperatively. These clinical data are the most complete to date for comparing the Nucleus speech processing strategies.
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    Cochlear implant speech processing for severely-to-profoundly deaf people
    Clark, Graeme M. ( 1996)
    A cochlear implant is a device which restores some hearing in severely-to-profoundly deaf people when the organ of Corti has not developed or is destroyed by disease or injury to such an extent no comparable hearing can be obtained with a hearing aid. When the organ of Corti is severely malfunctioning or absent, sound vibrations cannot be transduced into temporo-spatial patterns of action potentials along the auditory nerve for the coding of frequency and intensity. As a result, a hearing aid which amplifies sound, is of little or no use.
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    Psychophysical studies in children and the developing auditory system [Abstract]
    Busby, Peter A. ; Clark, Graeme M. ( 1995)
    A number of psychophysical studies have been conducted on cochlear implant patients who became deaf early in life. The implant prosthesis manufactured by Cochlear Pty. Limited was used. The aims of these studies have been to compare the performance of early-deafened and postlinguistically deafened adult patient groups, and to determine any relationships between the performance of early-deafened patients and variables that may influence performance, such as duration of deafness and age at implantation. The studies have also been concerned with the development of appropriate test procedures for early-deafened patients, who vary considerably in age arid cognitive ability.
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    Temporal and entrainment response properties of anteroventral cochlear neurons to intra cochlear electrical stimulation in the cat [Abstract]
    Buden, S. V. ; Brown, M. ; Paolini, A. G. ; Clark, Graeme M. ( 1996)
    Frequency coding within the central auditory system involves both spatial and temporal components. The temporal coding of sound is based on the phase or time locked neural response seen to low frequency acoustic stimuli. The ability of neurons to respond in a sustained time locked manner will determine the degree of encoded temporal frequency information.
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    A mathematical analysis of sound coding in the auditory nerve: spatiotemporal summing mechanisms
    Bruce, I. C. ; Irlicht, L. S. ; Clark, Graeme M. ( 1995)
    An understanding of mechanisms by which the human auditory system codes acoustical information has application to automated speech recognition and cochlear implants. In this paper, we formulate and analyse a mathematical model of the auditory system. The results are used to evaluate certain key theories of intensity and frequency coding.
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    The temporal and entrainment response properties of neurons to intracochlear electrical stimulation [Abstract]
    Brown, Mel ; Buden, S. V. ; Paolini, A. G. ; Clark, Graeme M. ( 1996)
    Understanding temporal coding in the central auditory pathway following electrical stimulation is important for further development of speech processing strategies and will also lead to a better understanding of temporal coding of acoustic stimuli. The temporal coding of sound frequency is based on the phase or time locked neural response seen to low frequency acoustic stimuli. The ability of neurons to respond in a time locked manner may determine the degree of encoded temporal frequency information. Single unit electrophysiological studies have shown that the degree of response synchrony to charge balanced biphasic electrical stimuli is far greater than that seen to acoustic stimuli.