- Graeme Clark Collection
Graeme Clark Collection
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ItemElectrical stimulation of residual hearing in the implanted cochleaClark, Graeme M. ; McAnally, K. I. ; Black, R. C. ; Shepherd, R. K. ( 1995)The average profoundly deaf person using a cochlear implant can now understand more speech than some severely to profoundly deaf people who use a hearing aid. For this reason there will be an increasing need to consider implanting people with residual hearing. In many of these people there could be significant hearing in the operated ear, as a majority of severely to profoundly deaf people are likely to have a symmetrical hearing loss. When three frequency average hearing thresholds were measured on 219 pensioners from the Australian National Acoustic Laboratories (H. Dillon, unpublished findings), 64% had less than a 10-dB difference between thresholds in each ear.
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ItemCochlear implantation: osteoneogenesis, electrode-tissue impedance, and residual hearingClark, Graeme M. ; Shute, S. A. ; Shepherd, R. K. ; Carter, T. D. ( 1995)This study was undertaken to find out how new bone is produced in the implanted cochlea, and the effects of fibrous tissue and new bone growth on electrode-tissue impedance. This knowledge is essential, as bone and fibrous tissue in the cochlea could account for variations in patients' speech perception performance. The study was also carried out to examine the effects of implantation on residual hearing. This information is also important, as cochlear implant speech perception results in profoundly deaf people are now better on average than severely or profoundly deaf people obtain with a hearing aid. Consequently, more people will need to be considered for cochlear implantation in ears with some residual hearing. In this case we need to know to what extent residual hearing is affected by implantation. (From Introduction)
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ItemEffect of chronic electrical stimulation on cochlear nucleus neuron size in normal hearing kittensNi, Daofeng ; Seldon, H. Lee. ; Shepherd, Robert K. ; Clark, Graeme M. ( 1993)Very young cochlear-implant candidates may have undetected islands of residual hearing. Would the maturation of these functioning auditory neurons be affected by chronic cochlear stimulation? This was tested by examining neuron sizes in the cochlear nuclei of young, normal hearing kittens with and without chronic cochlear stimulation. Six animals received bilateral intra-or extracochlear implants and were electrically stimulated unilaterally for periods of 1,000-1,500 hours. After sacrifice, cross-sectional areas of approximately 11,000 neuron somata in the cochlear nuclei were measured with an image-analysis system. There were statistically significant differences between stimulated and unstimulated nuclei, especially the posteroventral cochlear nucleus (PYCN), in individual cats, but the directions of the differences were inconsistent. Overall, there was no significant effect of electrical stimulation on soma size. These results indicate that chronic electrical stimulation of the auditory nerve has no positive or negative trophic effects on otherwise innervated, maturing cochlear nucleus neurons.