title: Current steering and results from novel speech coding strategies.
abstract: OBJECTIVE
  Advanced Bionics' cochlear implants have independent current sources that can share stimulation current between 2 contacts (Current Steering). By stimulating 2 adjacent electrodes with different weights, different pitches can be evoked, allowing to increase the number of processing channels.
  
  
  METHODS
  A counterbalanced crossover design was used to compare 3 different current steering implementations to the clinical HiRes strategy.
  
  
  METHODS
  The study was a prospective, within-subject, repeated-measure experiment.
  
  
  METHODS
  The study group consisted of 8 postlingually deaf subjects with a minimum of 12-month experience in HiRes.
  
  
  METHODS
  The following programs were evaluated: 1) a Fast Fourier Transformation (FFT)-based current steering implementation with 120 stimulation sites; 2) the same current steering implementation but with 16,000 stimulation sites; and 3) a current steering implementation based on a sinusoidal decomposition of the original signal with 16,000 stimulation sites.
  
  
  METHODS
  Speech perception tests in quiet and in Comité Consultatif International Télégraphique et Téléphonique (CCITT) noise, as well as with competing talker; an adaptive test of the frequency difference limen; a Quality Assessment Questionnaire.
  
  
  RESULTS
  Current results do not show any improvement in speech perception for a certain current steering strategy compared with HiRes. However, when selecting the optimal current steering strategy, subjects could achieve a significant benefit compared with the clinical HiRes. In addition, the frequency difference limen could be reduced significantly at 1,280 Hz.
  
  
  CONCLUSIONS
  Current steering seems to have the potential to improve both understanding in adverse listening situations and frequency resolution. However, the optimal implementation needs further investigation.
authors.affiliation: Department of Otolaryngology, Medical University of Hannover, Hannover, Germany. buechner@hoerzentrum-hannover.de
authors.forename: Andreas
authors.initials: A
authors.lastname: Buechner
authors.forename: Martina
authors.initials: M
authors.lastname: Brendel
authors.forename: Beate
authors.initials: B
authors.lastname: Krüeger
authors.forename: Carolin
authors.initials: C
authors.lastname: Frohne-Büchner
authors.forename: Waldo
authors.initials: W
authors.lastname: Nogueira
authors.forename: Bernd
authors.initials: B
authors.lastname: Edler
authors.forename: Thomas
authors.initials: T
authors.lastname: Lenarz
mesh_terms: D000328:Adult; D000465:Algorithms; D003054:Cochlear Implants; D018592:Cross-Over Studies; D003638:Deafness / Q000523:psychology / Q000628:therapy*; D004567:Electrodes, Implanted; D005260:Female; D005583:Fourier Analysis; D006801:Humans; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D010898:Pitch Perception; D011446:Prospective Studies; D011474:Prosthesis Design; D013067:Speech Perception / Q000502:physiology*