Graeme Clark Collection
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ItemThe University of Melbourne/Nucleus cochlear prosthesis( 1988)This is a review of research to develop the University of Melbourne/Nucleus cochlear prosthesis for patients with a profound-total hearing loss. A more complete review can be obtained in Clark et al. A prototype receiver-stimulator and multiple-electrode array developed at the University of Melbourne was first implanted in a postlingually deaf adult patient with a profound-total hearing loss on 1 August 1978. A speech processing strategy which could help this patient understand running speech, especially when combined with lipreading was developed in 1978 following initial psychophysical studies. A prototype wearable speech processor was fabricated in 1979, that could provide significant help for the first two patients in understanding running speech when used in combination with lipreading compared with lipreading alone, and it also enabled them to understand some running speech when using electrical stimulation alone. An implantable receiver-stimulator and wearable speech processor embodying the principles of the prototype devices were then produced for clinical trial by the Australian biomedical firm, Nucleus Ltd, and its subsidiaries, Cochlear Pty Ltd and Cochlear Corporation. This cochlear implant was initially clinically trialled on six patients at The Royal Victorian Eye & Ear Hospital in 1982, and shown to give similar results to those obtained with the prototype device. In view of these findings a clinical trial was carried out for a Premarket Approval Application to the US Food and Drug Administration (FDA), and extended to a number of centres in the US, Canada, and West Germany. This clinical trial confirmed that patients could understand running speech when electrical stimulation was combined with lipreading, and that some patients could also understand running speech when using electrical stimulation alone. Today, more than 600 patients world-wide are using cochlear implants developed from the research described in this paper.
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ItemCochlear implant and otitis media: a pilot study to assess the feasibility of pseudomonas aeruginosa and streptococcus pneumoniae infection in the cat( 1984/85)An experimental model for the induction of otitis media in cats is described using pseudomonas aeruginosa and streptococcus pneumoniae. Until now the cat has been regarded as being resistant to streptococcus pneumoniae infections, whereas pseudomonas aeruginosa is known to cause a most virulent otitis media in this animal. A successful inoculation using streptococcus pneumoniae, however, can be achieved by direct inoculation of a highly concentrated suspension of microorganisms in the bulla, retention of the organisms by Gelfoam®, and enhancement of virulence by intrapertioneal inoculation in mice. The model promises to be an important contribution in studying the effects of pneumococcal otitis media in Cochlear Implants.
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ItemSurgery for an improved multiple-channel cochlear implant( 1984)An improved multiple-channel cochlear implant has been developed. The titanium container with enclosed electronics, the receiver coil and the connector are embedded in medical-grade Silastic. The upper half of the implant has a diameter of 35 mm and a height of 4.5 mm. and the lower half a diameter of 23 mm and a height of.5 mm. The electrode array has also been designed to reduce the possibility of breakage due to repeated movements over many years. The surgery involves drilling a bed in the mastoid bone for the receiver-stimulator, and fixing the proximal electrode under the mastoid cortex. Gentle insertion of the electrode array through the round window and along the seala tympani is achieved with a specially designed microclaw.
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ItemElectrical stimulation of the auditory nerve: stimulus induced reductions in neural excitability [Abstract]( 1987)Electrical stimulation of the auditory nerve elicits highly synchronised neural activity (Javel et al., in press). As the stimulus current is increased the neural response becomes highly deterministic with every current pulse eliciting a spike even at stimulus rates of 600-800 pulses per second (pps). Our previous acute experimental studies have shown that high stimulus rates (> 200 pps) and high stimulus currents (> 1.0 mA) can result in temporary and sometimes permanent reductions in the excitability of the auditory nerve (Shepherd and Clark, 1986). The present study was designed to examine the mechanisms underlying these stimulus induced reductions in excitability. These results will have implications for the maximum safe and effective stimulus rates that can be employed in cochlear implants.