Graeme Clark Collection
Permanent URI for this collection
Search Results
1 - 10 of 41
-
ItemChronic electrical stimulation of the auditory nerve at high rates: I. Effect on residual hearing [Abstract]( 1996)In addition to direct excitation of auditory nerve fibres, cochlear implant patients with small amounts of residual hearing may receive important additional auditory cues via electrophonic activation of hair cells 1. Before incorporating electrophonic hearing into speech processing strategies, the extent of hair cell survival following cochlear implantation must first be determined. We have recently demonstrated widespread survival of hair cells apical to electrode arrays implanted for periods of up to three years, the present report describes the effects of chronic electrical stimulation on hair cell survival.
-
ItemChronic electrical stimulation of the auditory nerve at high rates: II. Cochlear pathophysiology [Abstract]( 1996)A major factor in the improved performance of cochlear implant patients has been the use of high stimulus rate speech processing strategies. While these strategies show clear clinical advantage, we know little of their long-term safety. Indeed, recent studies have indicated that high stimulus rates at intensities above clinical limits, can result in neural damage as a result of prolonged neuronal hyperactivity. The present study was designed to evaluate the effects of chronic electrical stimulation of the auditory nerve at high rates, using intensities within clinical limits.
-
ItemIntracellular responses of anteroventral cochlear nucleus neurones to intracochlear electrical stimulation in the rat [Abstract]( 1996)The anterior division of the ventral cochlear nucleus (AVCN) is the first relay station of the auditory pathway. Currently little is known about the intracellular physiological responses of neurones in the AVCN to electrical stimulation of the cochlea. We investigated the effect of cochlear electrical stimulation in the rat AVCN using in vivo intracellular recordings. Male rats were anaesthetised with urethane (1.3g/kg i.p), placed in a stereotaxic frame, the crania and dura removed and the cochlear nucleus exposed.
-
ItemElectrophonically driven single unit responses of the anteroventral cochlear nucleus in cat [Abstract]( 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.
-
ItemComparison and alternate designs for peri-modiolar electrode arrays: insertion trauma and position [Abstract]( 1997)While it has been shown that the straight but flexible banded electrode array can be safely inserted into the scala tympani of the human cochlea, histological studies have revealed that the array lies along the outer walll.2. Since a profound total hearing loss is generally associated with a moderate to complete degeneration of the spiral ganglion peripheral process, these electrodes lie some distance from their target neural population -the spiral ganglion soma -located within Rosenthal's canal.
-
ItemThe use of click-ABR and steady state evoked potentials for hearing assessment in young cochlear implant candidates [Abstract]( 1997)The accurate assessment of hearing thresholds in prospective cochlear implant candidates is essential. As the minimum age of implantation has reduced, audiologists have been faced with the complicated task of obtaining precise audiometric information in children whose immaturity may severely restrict the assessment process. Clearly for these young candidates, there is a place for a reliable, objective measure of residual hearing in the pre-operative test battery. This paper examines the degree of accuracy with which the click-ABR and the steady-state evoked potential (SSEP) techniques can provide estimates of hearing level in subjects with several profound hearing loss.
-
ItemImplantation of the new nucleus C1-3 receiver stimulator and electrode array [Abstract]( 1997)There is an important need to fix the cochlear implant electrode array at a site close to the cochlea, so that the electrode will not slide out, or be subject to differential movement with growth changes. Fixation sites have been in the region of the posterior root of the zygoma and the floor of the antrum. Fixation has been by Dacron mesh ties platinum wire ties, or clips inserted with-special instruments. Biological cements have previously been tried but found to be toxic. The most ideal site is in the region of the cochleostomy.
-
ItemTemporal coding for sound and tempor-spatial patterns of electrical stimulation [Abstract]( 1997)The anterior division of the ventral cochlear nucleus (AVCN) is the first relay station of the auditory pathway. It receives auditory information via the auditory nerves emanating from the cochlea. Electrical stimulation via current cochlear implants [ ] does not lead to responses at the cochlear nucleus that exactly match tho elicited by comparable auditory stimulation. Complex temporal patterns of electrical stimulation may provide a better simulation of the acoustic input.
-
ItemIntracellular responses of ventral cochlear nucleus neurones to acoustic stimulation in the rat( 1997)The ventral cochlear nucleus (VCN) is the first relay station of the auditory pathway. Presently, little is known about the acoustically evoked intracellular response of neurones in the VCN. We investigated the effect of acoustic stimulation on neurones in the rat VCN using in vivo intracellular recordings and dye-filling. In male rats anaesthetised with urethane (1.3g/kg i.p) microelectrodes containing 1M potassium acetate, or with 4% neurobiotin, were inserted into the VCN. Stable impalements were made from 37 neurones classified as having a Primary-like (n=13), Primary-like with notch (n=4) and Chopper (n=20) response to acoustic stimulation (50 ms pure tones, 5 ms r/f time, 0.2 Hz repetition).
-
ItemAetiology of hearing loss in children presenting for cochlear implantation and outcomes [Abstract]( 1997)The aetiology of hearing loss has a significant bearing on the likely outcome of cochlear implantation and therefore is an important consideration in patient selection and workup. Disease processes which result in sensorineural hearing loss may be associated with other structural or functional neurological disorders, in addition to 'damage to the cochlea and auditory pathways.
- 1 (current)
- 2
- 3
- 4
- 5