Graeme Clark Collection

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    The development of speech perception in children using cochlear implants: effects of etiologic factors and delayed milestones
    PYMAN, BRIAN ; Blamey, Peter J. ; Lacy, Peter ; Clark, Graeme M. ; DOWELL, RICHARD ( 2000)
    Hypothesis: Speech perception outcomes for cochlear implantation of children vary over a wide range, and it is hypothesized that central pathologic states associated with certain causes of hearing impairment account for a substantial part of the variance. Study Design: A retrospective analysis was carried out to ascertain the relationships between speech perception, etiologic factors, and central pathologic states as indicated by preoperative delayed motor milestones and/or cognitive delays. Setting: Data were obtained from the pre-and postoperative records of patients attending a hospital cochlear implant clinic. Patients: Results for 75 consecutive patients up to age 5 years who underwent implantation were included in the study. Intervention: Patients received a 22-electrode cochlear prosthesis and were seen by the clinic for regular tune-up and assessments. Home-and school-based habilitation was recommended by the clinic. Main Outcome Measures: Speech perception measures were classified on a five-point scale to allow for different evaluation procedures at different ages and developmental stages. Results: The incidence of motor and cognitive delays were fairly evenly spread across etiologic factors, except for cytomegalovirus, which had a much higher than average incidence. Children with motor and/or cognitive delays were significantly slower than other children in the development of speech perception skills after implantation. Etiologic factors did not have a statistically significant effect on speech perception outcome. Conclusions: It is likely that central pathologic states account for a substantial part of the variance among children using cochlear implants. Specific indicators of central pathologic states should be used to assess a child's prognosis in preference to less specific information based on etiologic factors alone.
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    Building the bionic ear
    Clark, Graeme M. ( 2000)
    When I began my cochlear-implant research in 1967, one could do nothing to help profoundly deaf people hear. In normal hearing, hair cells in the cochlea, the snail-shaped inner ear, transduce sound vibrations into electrical signals. These signals produce patterns of electrical responses in the auditory pathways that convey the frequency and intensity of the sound to the brain. The profoundly deaf, however, have lost their hair cells, so even amplifying sound with a hearing aid fails to transmit information that the brain can interpret as sound.
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    Cochlear implants in children
    Clark, Graeme M. ( 1995)
    Cochlear implants are devices that are used to artificially excite hearing nerves with patterns of stimulation that convey speech information and environmental sounds when a person's inner ear has been destroyed by disease or not developed at birth. In this situation they cannot benefit from the amplification of sound with a hearing aid.
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    Articulation accuracy of children using an electrotactile speech processor
    Galvin, Karyn L. ; Cowan, Robert S. C. ; Sarant, Julia Z. ; Tobey, Emily A. ; Blamey, Peter J. ; Clark, Graeme M. ( 1995)
    Objective: Use of wearable tactile speech perception devices is suggested to help overcome the difficulties in speech production resulting from severe and profound hearing impairment in children. This suggestion is based on the assumption that subjects can use tactile input in isolation, or in combination with information from residual aided hearing, to monitor and modify their speech. The present study evaluated the benefits to articulation provided through use of a multichannel electrotactile device (“Tickle Talker™”). Design: Six profoundly hearing-impaired children were videotaped speaking with the Tickle Talker on and with the Tickle Talker off during conversations with their audiologist. Five of the subjects also wore their binaural hearing aids during all recorded conversations. The number of vowels, consonants, and overall phonemes correctly articulated by each child in the two conditions were compared. Results: One subject improved articulation of initial consonants and initial phonemes; one subject improved articulation of total vowels, total consonants, initial consonants, total phonemes, and initial phonemes; and a third subject improved articulation of total vowels and medial phonemes. Conclusions: Use of on-line tactile feedback from the Tickle Talker may benefit the articulation accuracy of some children, and the device may therefore be suitable to use with children who have not responded to more traditional speech training techniques.
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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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    Cochlear implants in children: the value of cochleostomy seals in the prevention of labyrinthitis following pneumococcal otitis media
    Dahm, M. C. ; Webb, R. L. ; Clark, Graeme M. ; Franz, B. K-H. ; Shepherd, R. K. ; Burton, M. J. ; ROBINS-BROWNE, R. ( 1995)
    Cochlea implantation at an early age is important in rehabilitating profoundly hearing impaired children. Given the incidence of pneumococcal otitis media in young children, there has been concern that cochlear implantation could increase the possibility of otitis media, leading to labyrinthitis in this age group. Clinical experience has not indicated an increase in the frequency of otitis media and labyrinthitis in implanted adults or children over two years. However, labyrinthitis has occurred in implanted animals with otitis media. In order to assess the impact of cochlear implants on the occurrence of labyrinthitis, pneumococcal otitis media was induced in 21 kittens. Thirty-two kitten cochleas were implanted, of which 9 had a fascial graft and 9 a Gelfoam® graft. Nine control cochleas were unimplanted. Labyrinthitis occurred in 44% of unimplanted controls. 50% of implanted ungrafted cochleas, and 6% of implanted grafted cochleas. There was no statistically significant difference between the incidence of labyrinthitis in the implanted cochleas and the unimplanted controls. However there was a statistically significant difference between the ungrafted and grafted cochleas, but not between the two types of graft.
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    Anatomic and surgical considerations in the design of a new receiver-stimulator suitable for implantation in young children
    Pyman, B. C. ; Clark, Graeme M. ( 1995)
    The anatomy of the temporal bone was studied to determine the optimal shape and dimensions of a new receiver-stimulator for use in young children even less than 12 months of age. There was a need to make the receiver-stimulator electronic package smaller so that it could be placed within the mastoid cavity, and the antenna wider, for more efficient power and data transmission. The antenna needed to conform to the smaller radius of a young child's skull. Anatomic dissections were carried out on skulls of children from 3 to 11 months of age to establish the variations in dimensions relevant for implantation. Prototype implant designs were evaluated in these skulls and it was found that the maximum thickness the anterior section of the receiver-stimulator should be was 5.5 mm, and its maximum width, 18 mm. It was found that a prototype electronics package with these dimensions could be fitted comfortably into the average skull of an 8-month-old child. A particular constraint was the depth of the bone over the sigmoid sinus and middle fossa. The radius of curvature of the skull of young children also required the package to be bent in its center at an angle of 160°.
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    Phonetic and phonological changes in the connected speech of children using a cochlear implant
    Grogan, M. L. ; Barker, E. J. ; Dettman, S. J. ; Blamey, P. J. ( 1995)
    In excess of 5,000 children, with profound hearing impairment, have received a cochlear implant hearing device. Researchers have recently begun to study the speech production skills of these children.1-6 This topic is of interest because the speech of young prelingually or postlingually deaf children is in a constant state of development. The effectiveness of the implant, therefore, must be measured in its ability to provide enough auditory information for the child to develop intelligible speech. This is in addition to the maintenance of intelligible speech in the case of older postlingually deaf children or adults. The aim of the present study was to investigate some characteristics of the connected speech of a selected group of children from the University of Melbourne Cochlear Implant Programme. More specifically, the study aimed to determine how these characteristics changed over time. Studies of conversational speech samples are useful in that they do not depend on imitation yet they do reflect the child's everyday communication skills and are sensitive to co-articulatory effects. Analyses performed on the preoperative and postoperative data aimed to detect both the phonetic and phonologic changes in the segmental features of speech. The following questions were addressed: 1) What was the pattern of change in the phonetic inventories from before to after implantation? 2) Was there a difference in the correct production of consonants depending on their position in the word? 3) Did the group performance for correct production of phonemes change significantly from before to after implantation? 4) Did performance change over time for individuals? 5) What were the most common phonologic processes and was there a significant reduction in any of these processes from before to after implantation?
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    Potential and limitations of cochlear implants in children
    Dowell, R. C. ; Blamey, P. J. ; Clark, Graeme M. ( 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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    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.