Graeme Clark Collection
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ItemPreoperative residual hearing as a predictor of postoperative speech scores for adult cochlear implant users [Abstract]( 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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ItemA clinical report on vocabulary skills in cochlear implant users [Abstract]( 1994)Receptive vocabulary results are reported for 32 children, adolescents and prelinguistically deafened adults implanted with the 22-electrode cochlear implant at the Melbourne Cochlear Implant Clinic. Age at implantation ranged from 2 years, 6 months to 20 years and implant use ranged from 1 year to 7 years, 8 months. There were significant gains from pre- to postoperative assessments on the Peabody Picture Vocabulary Test (PPVT) for the majority of subjects. Rates of improvement found are compatible with previous reports on smaller numbers of implant users, but cannot be attributable unambiguously to use of the implant. The group postoperative performance was significantly higher than mean preoperative performance (n =25). The relationship of variables such as duration of implant use, duration of profound deafness and speech perception ability to improvement on the PPVT is discussed. Expressive vocabulary results on the Renfrew Word Finding Vocabulary Scale are reported for 11 of the subjects. Less substantial gains were made on this measure.
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ItemCombined cochlear implant and speech processing hearing aid for implant users with a severe to profound hearing loss in the contralateral ear [Abstract]( 1994)The bimodal device was developed for cochlear implant users who simultaneously wear a hearing aid in the opposite ear having residual hearing of a severe to profound degree. The aim was to create a single device to provide both input signals in a more compatible manner and thus maximise use of the individual's total hearing capabilities. The acoustic component of the bimodal device is very flexible and can implement various speech processing strategies with speed, ease and precision. The Frequency Response Tailoring strategy utilises three filters to fit a frequency gain curve to within 1-2 dB of that desired. Modifications at discrete frequencies, ranges or slopes can be readily made. The Peak Sharpening or Spectral Enhancement strategy amplifies the formant peaks in speech for potential improvement of formant resolution and speech perception in the presence of background noise. The Resynthesis strategy presents specifically selected components of speech in selected combinations and includes the ability to transpose higher frequency information to lower frequency ranges for individuals with no aidable high frequency hearing levels. Different fits can be quickly and easily interchanged for comparison and evaluation and subsequent modifications indicated can be readily effected. Any combination of acoustic and implant speech processing strategy can be presented to optimise speech perception for the individual user.
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ItemA clinical report on speech production of cochlear implant users [Abstract]( 1994)Speech production results are reported for a group of 15 children, adolescents and prelinguistically deafened adults implanted with the 22-electrode cochlear implant. Age at implantation ranged from 5 years to 20 years and implant experience ranged from 1 year to 4 years, 7 months. On a speech intelligibility test using sentences seven implant users improved significantly over time. Mean group performance (n = 11) improved from 18% preoperatively to 43% postoperatively. Similarly on a test of articulation, eight implant users improved significantly over time and the group mean postoperative performance (n = 11) exceeded the preoperative performance (55% compared to 38%). This group effect was significant for consonants and blends but was nonsignificant for vowels. Improvements occurred for front, middle and back consonants, for stops, nasals, fricatives and glides and for voiceless and voiced consonants. Three implant users showed no significant gain on either test. The results suggest complex relationships between speech production performance and sensory information provided by a multichannel implant.