Threshold and channel interaction in cochlear implant users: evaluation of the tripolar electrode configuration.
The efficacy of cochlear implants is limited by spatial and temporal interactions among channels. This study explores the spatially restricted tripolar electrode configuration and compares it to bipolar and monopolar stimulation. Measures of threshold and channel interaction were obtained from nine subjects implanted with the Clarion HiFocus-I electrode array. Stimuli were biphasic pulses delivered at 1020 pulses/s. Threshold increased from monopolar to bipolar to tripolar stimulation and was most variable across channels with the tripolar configuration. Channel interaction, quantified by the shift in threshold between single- and two-channel stimulation, occurred for all three configurations but was largest for the monopolar and simultaneous conditions. The threshold shifts with simultaneous tripolar stimulation were slightly smaller than with bipolar and were not as strongly affected by the timing of the two channel stimulation as was monopolar. The subjects' performances on clinical speech tests were correlated with channel-to-channel variability in tripolar threshold, such that greater variability was related to poorer performance. The data suggest that tripolar channels with high thresholds may reveal cochlear regions of low neuron survival or poor electrode placement.
Bierer
Julie Arenberg
JA
Department of Speech and Hearing Sciences, University of Washington, 1417 NE 42nd Street, Box 354875, Seattle, Washington 98105-6246, USA. jbierer@u.washington.edu
D000162:Acoustics / Q000295:instrumentation; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001307:Auditory Perception / Q000502:physiology*; D001309:Auditory Threshold / Q000502:physiology; D016923:Cell Death; D003051:Cochlea / Q000473:pathology / Q000601:surgery; D003054:Cochlear Implants; D004567:Electrodes, Implanted; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009474:Neurons / Q000473:pathology