• Andreas Buechner, Martina Brendel, Beate Krüeger, Carolin Frohne-Büchner, Waldo Nogueira, Bernd Edler, and Thomas Lenarz.
• Department of Otolaryngology, Medical University of Hannover, Hannover, Germany. buechner@hoerzentrum-hannover.de
• Otol. Neurotol. 2008 Feb 1; 29 (2): 203-7.

ObjectiveAdvanced 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.Study DesignA counterbalanced crossover design was used to compare 3 different current steering implementations to the clinical HiRes strategy.SettingThe study was a prospective, within-subject, repeated-measure experiment.PatientsThe study group consisted of 8 postlingually deaf subjects with a minimum of 12-month experience in HiRes.InterventionThe 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.Main Outcome MeasuresSpeech 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.ResultsCurrent 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.ConclusionCurrent steering seems to have the potential to improve both understanding in adverse listening situations and frequency resolution. However, the optimal implementation needs further investigation.

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