title: Effect of electrode impedance on spread of excitation and pitch perception using electrically coupled "dual-electrode" stimulation.
abstract: OBJECTIVE
  In newer-generation Cochlear Ltd. cochlear implants, two adjacent electrodes can be electrically coupled to produce a single contact or "dual electrode" (DE). The goal of the present study was to evaluate whether relatively large impedance differences (>3.0 kOhms) between coupled electrodes affect the excitation pattern and pitch percepts produced by the DE.
  
  
  METHODS
  Fifteen electrode pairs in six recipients were tested. Neural spread-of-excitation patterns and pitch perception were measured for adjacent physical electrodes (PEs) and the resulting DE to determine if the lower-impedance PE in the pair dominates the DE response pattern. The results were compared with a "normative sample" (impedance differences <3.0 kOhms) from two earlier studies.
  
  
  RESULTS
  In general, spread-of-excitation patterns for DEs more closely approximated those of the lower-impedance PE in each pair. The DE was more easily distinguished in pitch from the higher-impedance PE than the lower-impedance PE. The electrically evoked compound action potential and perceptual results generally differed from those of the normative group.
  
  
  CONCLUSIONS
  Impedance differences between adjacent PEs should be considered if DE stimulation is implemented in future research studies or clinical coding strategies.
authors.affiliation: Boys Town National Research Hospital, Lied Learning and Technology Center, Omaha, Nebraska, USA.
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Hughes
authors.forename: Jacquelyn L
authors.initials: JL
authors.lastname: Baudhuin
authors.forename: Jenny L
authors.initials: JL
authors.lastname: Goehring
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000293:Adolescent; D000328:Adult; D002648:Child; D019929:Cochlear Implantation; D003054:Cochlear Implants; D003638:Deafness / Q000534:rehabilitation*; D017097:Electric Impedance; D004558:Electric Stimulation; D004567:Electrodes, Implanted; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010898:Pitch Perception / Q000502:physiology*; D055815:Young Adult