Graeme Clark Collection

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End date: 2009 × Type: Book Item ×

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Now showing 1 - 5 of 5
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    Inner ear implants
    Clark, Graeme M. (Dekker, 2004)
    The cochlear implant is an electronic device that brings useful hearing to severely to profoundly deaf people through multiple-channel electrical stimulation of the auditory nerves in the inner ear. This is required if their inner ears are so badly damaged by injury and disease, or so inadequately developed, that they cannot provide sufficient hearing for communication, even when the sound is amplified with a hearing aid. By stimulating the nerve directly with patterns of electrical pulses, the implant bypasses the normal function of the sense organ of hearing in the inner ear to partially reproduce the coding of sound. It consists of a wearable speech processor that picks up sound with a microphone, analyzes the signal, and then sends it by radio waves to the implanted receiver stimulator, which decodes the message and stimulates the electrode wires inserted into the inner ear.
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    Steady state evoked potentials: a new tool for the accurate assessment of hearing in cochlear implant candidates
    Rance, G. ; Rickards, F. W. ; Cohen, L. T. ; Burton, M. J. ; Clark, Graeme M. ( 1993)
    Precise determination of residual hearing in prospective cochlear implant candidates is essential. As the minimum age of implantation for young children has reduced, the use of objective measures of hearing has become more important. At the University of Melbourne Cochlear Implant Clinic, steady state evoked potential (SSEP) assessments are routinely carried out on all candidates under the age of 5 years using a microcomputer and custom-designed hardware in the manner described by Cohen et al. [1].
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    Responses from single units in the dorsal cochlear nucleus to electrical stimulation of the cochlea
    O'Leary, S. J. ; Tong, Y. C. ; Clark, Graeme M. (Karger, 1993)
    An aim of the electrical stimulation strategy of a cochlear implant is to mimic the response of the auditory system to acoustic stimuli, so that hearing sensations generated by the implant can be recognisable and useful to the implantee. To help improve our understanding of how the brain responds to electrical stimulation of the auditory nerve we have examined the responses of dorsal cochlear nucleus (DCN) units to both acoustic and electrical stimulation of the cochlea in a hearing animal. This work extended our previous studies which have compared the responses to electrical and acoustic stimulation in the auditory nerve [1] and the ventral cochlear nucleus [2]. Our studies addressed two questions: (1) What are the responses of DCN units to electrical stimulation of the auditory nerve? (2) Was it possible to identify acoustic and electrical stimuli which generated similar responses from individual DCN units? By answering questions 1 and 2, it may be possible to deduce the electrical stimulus parameters which should be employed in cochlear implant speech processing strategies to mimic acoustic-like responses from neurons of the dorsal cochlear nucleus. The generality of observations from the cochlear nucleus could then be tested at other nuclei within the central auditory pathways.
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    Three-dimensional reconstruction of the cochlea and temporal bone
    Dahm, Markus C. ; Seldon, H. Lee ; Pyman, Brian C. ; Laszig, Roland ; Lehnhardt, Ernst ; Clark, Graeme M. (Karger, 1993)
    In recent years, cochlear implantation has become an established method for the auditory rehabilitation of profoundly deaf patients and is used in ever more and younger patients. High-resolution computed tomography is performed routinely on all prospective cochlear implant patients and provides important information about cochlear or mastoid pathology that will enable the surgeon to select a side for operation and alert him to surgical obstacles he might encounter [1-4]. In analysing the CT films he must still try to form a three-dimensional image in his mind by looking through a large number of different pictures [5]. Consequently, to make it easier to understand, we applied our own image analysis system to produce three-dimensional reconstructions of temporal bones from CT scans[6]. We focused on the use of this method for the preoperative examination and surgical planning for cochlear implantation as well as for our research purposes. This system and the results are presented here.
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    Current distributions of intracochlear electrodes in cats [Abstract]
    O'Leary, S. J. ; Black, R. C. ; Clark, Graeme M. (Monash University Press, 1983)
    A non-invasive technique, "two electrode mapping" has been developed to measure the current distribution of a multichannel electrode array within the feline scala tympani. An electrode’s current distribution is an important determinant of its ability to excite discrete neural groups. The electrode array, a “banded electrode” is a series of platinum rings, supported by a cylinder of silastic which fits freely into the scala tympani. All cats had normal hearing pre-operatively and were implanted through the round window. Hearing was normal within 10 dB after implantation, necessitating the presentation of 30-40 dB white noise to the implanted ear throughout experimentation to mask the electrophonic component (Black et al., 1983).