Graeme Clark Collection
Permanent URI for this collection
Search Results
1 - 3 of 3
-
ItemIntracellular responses of the rat anteroventral cochlear nucleus to intracochlear electrical stimulation( 1998)Unavailable due to copyright.
-
ItemChronic study on the neuronal excitability of the cochlear nuclei of the cat following electrical stimulation( 1998)To examine the safety of auditory brainstem prosthesis, the cat cochlear nuclei were implanted and stimulated chronically with bipolar surface electrodes using charge-balanced biphasic current pulses at rates of 250 pulses/s. The stimulation was continuous 16 h/day for up to 12 weeks. The electrically-evoked auditory brainstem response (EABR) was used to monitor neuronal excitability of the cochlear nuclei following the chronic electrical stimulation. The body weight, respiration, and body temperature of the cats were monitored throughout the experiment. The amplitudes and latencies of the EABR waves were measured fortnightly and compared before, during and after the electrical stimulation. The results showed that the respiration, body weight and body temperature of the cats remained within normal limits during the chronic stimulation. During the stimulation, no change was found in the EABR waveform, but a decreased threshold and wider dynamic range were observed after the stimulation. There was no significant change in the amplitudes and latencies of the EABR waves after stimulation. The present findings suggest that chronic bipolar electrical stimulation with surface electrodes at rates of 250 pulses/s is safe for neuronal excitability of the cochlear nuclei in the cat.
-
ItemAcute study on efficacy and safety of an auditory brainstem prosthesis( 1998)Patients with profound binaural sensorineural hearing loss can be treated with cochlear implantation. In recent years, patients who have lost the integrity of the auditory nerve between the spiral ganglion and the cochlear nucleus in the brainstem, and cannot benefit from a cochlear implant, have reported auditory sensations following direct stimulation of the cochlear nucleus with an auditory brainstem prosthesis. To examine the safety and efficacy of such a prosthesis, the cochlear nuclei of guinea-pigs were acutely implanted and stimulated unilaterally with bipolar surface electrodes using the parameters of human implants. The activation of the central auditory pathway by the prosthesis was demonstrated using the 2-deoxyglucose technique. There was broad 2-deoxyglucose labelling in the ipsilateral cochlear nucleus and bilaterally in the inferior colliculi, indicating unusual stimulation of the ipsilateral ascending pathway. Histological examination was performed on all cochlear nuclei. The volumes of cochlear nuclei and the neuron sizes and density in the cochlear nuclei were analysed with three-dimensional reconstruction techniques, and comparisons were made between the stimulated and unstimulated sides. No histological difference, either by direct visual observation or by statistical comparisons, was observed between the stimulated cochlear nuclei and the control sides. These results suggest that in the acute case the auditory brainstem prostheses can safely and effectively activate the auditory pathway in guinea-pigs.