Chronic electrical stimulation of the auditory nerve using high-surface area platinum electrodes [Abstract]
AuthorTykocinski, M.; Liu, X.; Clark, Graeme M.
Source TitleProceedings of the Australian Neuroscience Society
Document TypeConference Item
CitationsTykocinski, M., Liu, X., & Clark, G. M. (1999). Chronic electrical stimulation of the auditory nerve using high-surface area platinum electrodes [Abstract]. In Proceedings of the Australian Neuroscience Society, Hobart.
Access StatusOpen Access
This is an abstract of a paper from Proceedings of the Australian Neuroscience Society 1999 published by Australian Neuroscience Society. This version is reproduced with the permission of publisher.
Electrical stimulation using high surface area (HiQ) platinum (Pt) electrodes exhibit a lower electrode impedance, polarisation and direct current (DC) in vitro compared with standard (ST) Pt electrodes of the same geometric size. In the present study we investigated whether HiQ electrodes maintain these advantages in vivo. This could be important for the development of new arrays with an increased number of smaller electrodes. Under general anaesthesia (Ketamine 20 mg/kg and Xylazine 4mg/kg i.p.) five normal hearing cats were implanted bilaterally with a two-channel Pt scala tympani electrode array (4 HiQ, I ST array). Chronic electrical stimulation using charge balanced biphasic current pulses was delivered unilaterally via a transcutaneous leadwire connected to a backpack-stimulator for periods of up to 2400 hours. DC, stimulus current and electrode voltage waveforms were monitored twice daily and access resistance (Ra), electrode impedance (Zc) and polarisation (Zc-Ra) calculated (kΩ). Mean HiQ data were compared to ST data using Students t-test (*=p<0.05, **=p<0.001). Immediately following implantation both HiQ and ST-electrodes exhibited low impedance values (Ra: 1.06 vs 1.00, Zc: 1.24 vs 2.12*, and Zc-Ra: 0.18 vs 1.08**). Subsequently impedance increased, largely due to a rise in Ra (5.35 vs 6.8: Zc: 6.96 vs 9.80, and Zc-Ra: 1.61 vs 3.00*). At the end of the experiment the array was explanted and tested in saline (Ra: 0.63 vs 0.74*, Zc: 0.73 vs 1.90**, Zc-Ra: 0.10 vs 1.16**). These initial results suggests that intracochlear tissue growth increased the access resistance of both electrode designs. However, HiQ electrodes maintained not only a significantly lower polarisation, they also showed a lower average residual DC (23 vs 130 nA**) throughout the experiment.
Keywordsotolaryngology; cochlear implant; electrode design
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