Graeme Clark Collection
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ItemElectrical stimulation of residual hearing in the implanted cochlea( 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hearing thresholds were measured on 219 pensioners from the Australian National Acoustic Laboratories (H. Dillon, unpublished findings), 64% had less than a 10-dB difference between thresholds in each ear.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 hearing( 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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ItemTemporal coding of frequency: neuron firing probabilities for acoustic and electric stimulation of the auditory nerve( 1995)A better understanding of the temporal coding of frequency, and its application to electrical stimulation of auditory nerve fibers, should lead to advances in cochlear implant speech processing. Past research studies have suggested that the intervals between nerve action potentials are important in the temporal coding of frequency. For sound frequencies up to approximately 500 Hz, the shortest or predominant intervals between the nerve action potentials are usually the same as the periods of the sound waves. The intervals between each nerve action potential can be plotted as an interval histogram. Although there is evidence that the intervals between spikes are important in the temporal coding of frequency, it is not known up to what frequency this applies. It is also not known whether the information transmitted along individual fibers or an ensemble of fibers is important, to what extent the coding of frequency is interrelated with the coding of intensity, the relative importance of temporal and place coding for different frequencies, and finally, how well electrical stimulation can simulate the temporal coding of sound.