Graeme Clark Collection

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1992 - 1997 4
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End date: 1998 × Start date: 1990 × Type: Conference Item × Subject: cochlear implant × Subject: electrical stimulation × Subject: otolaryngology ×

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Now showing 1 - 4 of 4
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    Electrophonically driven single unit responses of the anteroventral cochlear nucleus in cat [Abstract]
    Morrison, N. A. ; Brown, M. ; Clark, Graeme M. ( 1996)
    Electrical stimulation of the cochlea results in both direct and electrophonic excitation of auditory nerve fibres. It has been proposed that electrophonic stimulation results from the creation of a mechanical disturbance on the basilar membrane which has properties similar those resulting from acoustic stimuli. Auditory nerve compound action potential (CAP) forward masking studies1 show the level of frequency specific electrophonic stimulation is highly correlated with the spectral energy of the electrical stimulus waveform. The level of spectral energy in pulsatile biphasic electrical stimuli decreases toward low frequencies suggesting the level of electrophonic stimulation will be diminished in the low frequency region of the cochlea.
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    Temporal coding in auditory neurons to electrical stimulation [Abstract]
    Brown, Mel ; Hocking, J. ; Clark, Graeme M. ( 1997)
    The temporal response of the auditory pathway following intracochlear electrical stimulation will reflect the level of encoded temporal information, which is important for the further developmentof cochlear implant speech processing strategies, and in tum lead to a better understanding of temporal coding of acoustic stimuli Temporal coding of sound frequencies is based on the phase or time locked neural response seen to low frequency acoustic stimuli. The ability of neurons to respond in a time locked manner may determine the degree of encoded temporal frequency information. Electrophysiological studies have shown that the degree of response synchrony to charge balanced biphasic electrical stimuli is far greater than that seen to acoustic stimuli. We have investigated the temporal response properties of single units in the anteroventral cochlear nucleus (AVCN) in the cat to rates of electrical stimulation up to 800 pulses/s.
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    Investigation of curved intracochlear electrode arrays [Abstract]
    Xu, Shi-Ang ; Xu, J. ; Seldon, H Lee. ; Shepherd, R. K. ; Clark, G. M. ( 1992)
    It has been demonstrated that the Melbourne/Cochlear multi-channel cochlear implant is safe and effective for use in profoundly-totally deaf patients. Recent studies have highlighted the importance of deaf insertion and placing the electrodes closer to the spiral ganglion neurons. In order to improve the electrode insertion depth and proximity to the modiolus, we have investigated curved electrode arrays. Prototypes of such arrays and their accessory inserter have been made. Trial insertions were performed on skeletonized cochleae of human temporal bones. The preliminary results showed that, when compared with conventional straight electrode arrays, the curved arrays could be inserted deeper and located closer to the modiolus. These findings indicate that the curved --.~ electrodes currently under investigation should result in a reduction in stimulus threshold and improve pitch perception and may also result in the use of more channels of stimulation.
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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. ( 1992)
    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 stimulation and electrical stimulation of the cochlea. This work extended our previous studies which have compared the responses to electrical and acoustic stimulation In the auditory nerve (Javel et al 1987, Ann. Otol. Rhinol. laryngeal. Suppl. 128, 96:2630) and the ventral cochlear nucleus (Shepherd et al 1988, NIH Contract NO1-NS-72342, 5th Quarterly Progress Report).