Graeme Clark Collection

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    A preliminary report on a multiple-channel cochlear implant operation
    Tong, Y. C. ; Black, R. C. ; Clark, Graeme M. ; Forster, I. C. ; Millar, J. B. ; O'Loughlin, B. J. ; Patrick, J. F. (Cambridge University Press, 1979)
    Intra-cochlear single-channel electrical stimulation has recently been attempted by Michelson (1971) and by House and Urban (1973). Douek et at. (1977) have described experiments with a single-channel promontory electrode system. It is generally accepted that a single-channel system is useful in conveying crude auditory information such as the presence of sounds and some prosodic features of speech (Bilger et al., 1977; Douek et al., 1977). (From Introduction)
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    Critical bands following the selective destruction of cochlear inner and outer hair cells
    Nienhuys, Terry G. W. ; Clark, Graeme M. ( 1979)
    Critical bandwidths and absolute intensity thresholds were measured in cats before and after kanamycin treatment which induced selective inner and outer hair cell losses. Hair cell losses were measured from cochleograms constructed from surface preparations of the organ of Corti. Results suggested that, for the test frequencies and stimulus intensities employed, critical bandwidths were not affected for frequencies tonotopically located in cochlear regions where only outer hair cells were lost. Critical bands were widened or not measurable only when inner hair cell losses exceeding 40% were also associated with complete loss of outer hair cells. The experiment suggests that cochlear frequency selectivity can be mediated by inner hair cells alone.
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    The surgery for multiple-electrode cochlear implantations
    Clark, Graeme M. ; Pyman, Brian C. ; Bailey, Quentin R. (Cambridge University Press, 1979)
    The multiple-electrode hearing prosthesis designed in the Departments of Otolaryngology and Electrical Engineering (UMDOLEE) at the University of Melbourne (Clark et al., 1977) has been miniaturized with hybrid circuitry so that, if design changes are necessary as a result of initial patient testing, they can be made at minimal cost. This results, however, in increased package dimensions which makes its placement and the design of the surgery more critical. This problem is increased by the fact that we have considered it important to be able to remove the package and replace it with another without disturbing the implanted electrode array, should the first receiver-stimulator fail or an improved design become available. This has meant the design of a special connector (Patrick, 1977; Clark et al., 1978) which adds to the dimensions of the implanted unit. In addition the placement of the coils for transmitting power and information has to be considered. Not only is it desirable to site the coils at a convenient location behind the ear to facilitate the placement and wearing of the external transmitter, but there should also be no relative movement between the coils and the electronic package. These design considerations have led to the sitting of the coils on top of the hermetically-sealed box, and further increased the height of the package. The dimensions of the package shown in Fig. 1 are length 42 mm, width 32 mm, height of connector 8.5 mm, height of receiver-stimulato unit 13 mm. The surgical considerations discussed are the result of a number of temporal bone and cadaver dissections, and the surgical implantation at The Royal Victorian Eye and Ear Hospital of the UMDOLEE unit in a specially-selected patient.
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    A cochlear implant round window electrode array
    Clark, Graeme M. ; Patrick, J. F. ; Bailey, Q. (Cambridge University Press, 1979)
    One important aspect of cochlear implantation is the placement of a multiple-electrode array close to residual auditory nerve fibres so that discrete groups of fibres can be stimulated electrically according to the place basis of frequency coding. Furthermore, in patients who are postlingually deaf these electrodes should lie in relation to the nerve fibres which are responsible for transmitting the frequencies which are important in speech comprehension, viz. 300-3,000 Hz. The method of electrode insertion should also ensure that there is no significant damage to auditory nerve fibres.
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    Frequency discrimination following the selective destruction of cochlear inner and outer hair cells
    Nienhuys, Terry G. W. ; Clark, Graeme M. ( 1978)
    http://www.sciencemag.org/cgi/content/abstract/199/4335/1356?ijkey=OnDf2slSrU.DE&keytype=ref&siteid=sci
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    A multiple-electrode cochlear implant
    Clark, Graeme M. ; Tong, Y. C. ; Bailey, Q. R. ; Black, R. C. ; Martin, L. F. ; Millar, J. B. ; O'Loughlin B. J. ; Patrick, J. F. ; Pyman, B. C. ( 1978)
    Interest in artificially stimulating the auditory nerve electrically for sensori-neural deafness was first sparked off by Volta in the 18th century. Count Volta, who was the first to develop the electric battery, connected up a number of his batteries to two metal rods which he inserted into his ears. Having placed the rods in his ears he pressed the switch and received "une secousse dans la tete" and perceived a noise like "the boiling of thick soup".
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    Design criteria of a multiple-electrode cochlear implant hearing prosthesis
    Clark, Graeme M. ; Black, R. C. ; Forster, I. C. ; Patrick, J. F. ; Tong, Y. C. ( 1978)
    Abstract not available due to copyright.
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    Frequency discrimination and critical bands following the selective destruction of cochlear inner and outer hair cells
    Nienhuys, T. G. W. ; Clark, Graeme M. ( 1977)
    The role of the inner and outer hair cells of the cochlea in frequency discrimination and critical band measurements is not clearly understood. There is, however, evidence for an interaction between the hair cells in threshold determinations (1) and frequency selectivity (2). Furthermore, although there is increasing evidence that a place theory is more importance than a periodicity theory in frequency coding the situation is still not clear, and the role of the inner and outer hair cells in frequency discrimination and critical band measurements should provide additional evidence to help clarify the situation.
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    Prosthetic devices for the management of patients with severe sensorineural deafness
    Clark, Graeme M. ; Tong, Y. C. ; Williams, A. ( 1977)
    It is estimated that 5-10% of patients with significant hearing loss do not get satisfactory help with a hearing aid. This means that in Australia there are about 5,000-10,000 people who need further treatment. Furthermore, a large number of these patients are born deaf and their proper management is critical if they are going to develop adequate speech and language. If these patients are going 10 perceive speech, the speech must be broken down into signals that can be used 10 stimulate the residual hearing, excite the auditory nerve fibres by electrical stimulation or stimulate another sensory system such as vision or the skin senses. These alternatives offer real hope for the patient with severe sensori-neural deafness as there is a great deal of redundancy in the speech signal. This is illustrated in Fig. 1 which shows the raw signal obtained on a cathode ray oscilloscope for the word "ear". It can be seen that there is an overall waveform envelope which is now thought to be quite important in speech perception. Inside the speech waveform there are waves of many shapes and sizes. Far too many for your eye to detect at a glance, and indeed too many for your ear to perceive. In fact, when you hear phonemes and words your brain only picks up key signals.
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    A multiple electrode cochlear implant
    Clark, Graeme M. ; Tong, Y. C. ; Black, R. ; Forster, I. C. ; Patrick, J. F. ; Dewhurst, D. J. (Cambridge University Press, 1977)
    It is generally agreed that if a cochlear implant hearing prosthesis is to enable a patient to understand speech, it must be a multiple-electrode system. In addition, stimulation of the auditory nervous system should approximate the patterns of neural excitation occurring in people with normal hearing, and this is especially important when a patient has previously experienced hearing. For this reason the correct application of electrophysiological principles to the design of a hearing prosthesis is desirable, and is discussed in this paper with special reference to a device developed in the Departments of Otolaryngology and Electrical Engineering at the University of Melbourne (UMDOLEE).