Graeme Clark Collection

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    Cognitive processing in children using cochlear implants: the relationship between visual memory, attention, and executive functions and developing language skills
    Surowiecki, Vanessa N. ; SARANT, JULIA ; MARUFF, PAUL ; Blamey, Peter J. ; Busby, Peter A. ; Clark, Graeme M. ( 2002)
    We performed this study to determine whether children using a cochlear implant performed differently from age- and gender-matched hearing aid users on 8 neuropsychological measures of visual memory, attention, and executive functioning. The study also examined whether differences in cognitive skills could account for some of the observed variance in speech perception, vocabulary, and language abilities of hearing-impaired children. In contrast to previous studies, our results revealed no significant cognitive differences between children who use a cochlear implant and children who use hearing aids. Partial correlation analysis indicated that the children’s visual memory skills, i.e., their recognition memory, delayed recall, and paired associative learning memory skills, correlated significantly with their language skills. When examined at a significance level of .01, attention and executive functioning skills did not relate to the children’s developing speech perception, vocabulary, or language skills. The results suggested that differences in visual memory skills may account for some of the variance seen in the language abilities of children using implants and children using hearing aids.
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    Speech perception in children using cochlear implants: prediction of long-term outcomes.
    Dowell, RC ; Dettman, SJ ; Blamey, PJ ; Barker, EJ ; Clark, GM (Informa UK Limited, 2002-03)
    A group of 102 children using the Nucleus multichannel cochlear implant were assessed for open-set speech perception abilities at six-monthly intervals following implant surgery. The group included a wide range of ages, types of hearing loss, ages at onset of hearing loss, experience with implant use and communication modes. Multivariate analysis indicated that a shorter duration of profound hearing loss, later onset of profound hearing loss, exclusively oral/aural communication and greater experience with the implant were associated with better open-set speech perception. Developmental delay was associated with poorer speech perception and the SPEAK signal coding scheme was shown to provide better speech perception performance than previous signal processors. Results indicated that postoperative speech perception outcomes could be predicted with an accuracy that is clinically useful.
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    Variation in speech perception scores among children with cochlear implants
    Sarant, JZ ; Blamey, PJ ; Dowell, RC ; Clark, GM ; Gibson, WPR (LIPPINCOTT WILLIAMS & WILKINS, 2001-02)
    OBJECTIVE: The objective of this study was to identify common factors affecting speech perception scores in children with cochlear implants. DESIGN: Speech perception data for 167 implanted children were collected at two cochlear implant centres in Melbourne and Sydney. The data comprised audition-alone scores on open-set word and sentence tests. Children were selected on the basis that they had a Nucleus 22-electrode cochlear implant. The average age of the children was 5 yr. Information was also collected about 12 factors that may have influenced speech perception scores for each child. Analysis of covariance was used to identify factors that significantly affected speech perception scores. Pearson pairwise correlation coefficients were also calculated for all factors analyzed. RESULTS: The analyses in this study identified factors that accounted for 51%, 34%, and 45% of the variance in phoneme, word and sentence perception scores. Scores decreased by 1.4 to 2.4% per year of profound deafness prior to implantation. Children who normally use oral communication scored significantly higher than children normally using sign or simultaneous oral and sign communication. Children implanted in Sydney scored higher on average than children implanted in Melbourne. CONCLUSIONS: The results show that a significant part of the variation in speech perception scores is systematically related to audiological and environmental factors for each child. The reasons for significant differences between children using different communication modes or from different clinics were not identified.
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    Generalisation of tactile perceptual skills to new context following tactile-alone word recognition training with the Tickle Talker
    Galvin, Karyn L. ; Blamey, Peter J. ; Cowan, Robert S. C. ; Oerlemans, Michael ; Clark, Graeme M. ( 2000)
    Abstract not available due to copyright.
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    The effect of language knowledge on speech perception: what are we really assessing?
    Sarant, Julia Z. ; Blamey, Peter J. ; Cowan, Robert S. ; Clark, Graeme M. ( 1997)
    Objective: The authors examined whether open-set speech perception scores are limited by knowledge of vocabulary and syntax and further considered whether remediation of vocabulary and syntax will increase open-set speech perception scores. Study Design: This was a repeated-measures study design in the setting of a primary (elementary) school for the hearing impaired. Patients: The study population was composed of three hearing-impaired children using Nucleus 22-channel cochlear implant. Intervention: Intervention used was language remediation sessions. Main Outcome Measures: The main outcome measures were assessment of auditory-alone speech perception benefit using open-set words and sentences and assessment of syntactic knowledge using the Test of Syntactic Ability. Outcome measures were applied before and after remediation. Results: Child 1 and child 2 showed a significant postremediation improvement in their overall scores on the Test of Syntactic Ability and in their ability to perceive words learned during remediation. Child I and child 2 also showed a significant improvement in their scores on a modified Bamford-Kowal-Bench open-set sentence test, which specifically targeted grammatical constructs trained in remediation sessions. Conclusions: Remediation of language knowledge deficits significantly improved open-set speech perception for two children, suggesting a need to include language remediation in cochlear implant habilitation programs.
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    Studies of prosody perception by cochlear implant patients
    Richardson, Louise M. ; Busby, Peter A. ; Blamey, Peter J. ; Clark, Graeme M. ( 1998)
    Prosodic information is conveyed to normally-hearing listeners by variations in acoustic fundamental frequency, amplitude envelope, and duration of speech segments. This study measured cochlear implant patients' sensitivity to these parameters in electrically coded speech. The psychophysical discrimination of electric parameters used to code prosodic information, were examined, together with prosody perception using speech processing strategies which modified the contributions of these parameters. Patients were implanted with the Cochlear Limited prosthesis and used the MPEAK speech processing strategy. In the psychophysical studies, difference limens were measured for steady-state and time-varying stimuli, of different pulse rates and pulse durations, over a series of different stimulus durations. These limens were obtained using an adaptive procedure which converged on the 50 per cent correct point. In the prosody perception studies, performance was measured for the MPEAK strategy and for strategies which modified the contributions of pulse rate and pulse duration. Data were collected for five tests of prosodic contrasts. Difference limens for steady-state pulse rates were larger at higher rates (17 per cent at 400 pulses/s) than at lower rates (6 per cent at 100 pulses/s). For some patients, limens for the time-varying pulse rates were larger than those for the steady-state pulse rates while for the other patients, the limens were similar. Difference limens for pulse duration were 0.3 dB, corresponding to 4 per cent of the dynamic range, for steady-state stimuli and doubled in size for the time-varying stimuli. Prosody perception performance was generally poorer for the modified strategies than for the MPEAK strategy, suggesting that the removal of information coded by pulse rate and pulse duration reduced the perception of prosodic contrasts.
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    Within-subject comparison of speech perception benefits for congenitally deaf adolescents with an electrotactile speech processor and a cochlear implant
    SARANT, JULIA ; COWAN, ROBERT ; BLAMEY, PETER ; GALVIN, KARYN ; Clark, Graeme M. ( 1996)
    This study assessed speech perception benefits for three congenitally deaf adolescents who used an electrotactile speech processor (Tickle Talkerâ„¢) and subsequently went on to use a Nucleus Minisystem 22 cochlear implant. Both devices provided significant and comparable benefits for all children in the device plus lipreading condition. All children benefited from the additional information provided by either the Tickle Talkerâ„¢ or the cochlear implant, and were able to perceive speech information with these devices that was not available through either aided residual hearing or lipreading. None of the three children were able to understand open-set words or sentences using either hearing aids alone or Tickle Talkerâ„¢ alone, without the aid of lipreading. Two of the children showed significant open-set speech perception benefits while using their cochlear implant alone.
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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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    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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    Within-subject comparison of speech perception benefits with a multiple-channel cochlear implant and tactile device
    Sarant, J. Z. ; Cowan, R. S. C. ; Blamey, P. J. ; Galvin, K. L. ; Clark, Graeme M. ( 1995)
    In order to adequately advise prospective cochlear implant patients and their families, a clinician must have a good knowledge of the potential for particular individuals to benefit from cochlear implants and other alternatives.