title: Evaluation of a cochlear-implant processing strategy incorporating phantom stimulation and asymmetric pulses.
abstract: OBJECTIVE
  To evaluate a speech-processing strategy in which the lowest frequency channel is conveyed using an asymmetric pulse shape and "phantom stimulation", where current is injected into one intra-cochlear electrode and where the return current is shared between an intra-cochlear and an extra-cochlear electrode. This strategy is expected to provide more selective excitation of the cochlear apex, compared to a standard strategy where the lowest-frequency channel is conveyed by symmetric pulses in monopolar mode. In both strategies all other channels were conveyed by monopolar stimulation.
  
  
  METHODS
  Within-subjects comparison between the two strategies. Four experiments: (1) discrimination between the strategies, controlling for loudness differences, (2) consonant identification, (3) recognition of lowpass-filtered sentences in quiet, (4) sentence recognition in the presence of a competing speaker.
  
  
  METHODS
  Eight users of the Advanced Bionics CII/Hi-Res 90k cochlear implant.
  
  
  RESULTS
  Listeners could easily discriminate between the two strategies but no consistent differences in performance were observed.
  
  
  CONCLUSIONS
  The proposed method does not improve speech perception, at least in the short term.
authors.affiliation: * MRC Cognition & Brain Sciences Unit , Cambridge , UK.
authors.forename: Robert P
authors.initials: RP
authors.lastname: Carlyon
authors.forename: Jolijn
authors.initials: J
authors.lastname: Monstrey
authors.forename: John M
authors.initials: JM
authors.lastname: Deeks
authors.forename: Olivier
authors.initials: O
authors.lastname: Macherey
mesh_terms: D000161:Acoustic Stimulation / Q000295:instrumentation* / Q000379:methods*; D000328:Adult; D000368:Aged; D003051:Cochlea; D019929:Cochlear Implantation / Q000379:methods*; D003054:Cochlear Implants; D003055:Cochlear Microphonic Potentials; D004566:Electrodes; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design; D011674:Pulse / Q000379:methods; D013067:Speech Perception
keywords: Cochlear implants; asymmetric pulses; phantom stimulation; speech perception