| Influence of widening electrode separation on current steering performance. | |
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MedLine Citation:
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PMID: 21063206 Owner: NLM Status: In-Data-Review |
Abstract/OtherAbstract:
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OBJECTIVES: : Current steering between adjacent electrodes makes it possible to create more spectral channels than the number of electrodes in an electrode array. With current steering on nonadjacent electrodes, called "spanning," it could be possible to bridge a defective electrode contact or potentially reduce the number of electrode contacts for the same level of access to the auditory nerve. This study investigates the effectiveness of spanning in terms of the number of intermediate pitches, loudness effects, and linearity of the current weighting coefficient (α) with respect to the perceived pitch. DESIGN: : Twelve postlingually deafened users of the HiRes90K cochlear implant with HiFocus1j electrode were randomly selected to participate in this study. Electrode contacts were selected at two locations in the cochlea, as determined on multislice computed tomography: 180° (basal) and 360° (apical) from the round window. For both cochlear locations, three psychophysical experiments were performed using simultaneous stimulation of electrode contacts. An adaptive staircase-based procedure was used. The number of intermediate pitches was assessed with a three-alternative forced choice (3AFC) pitch discrimination task, and the extent of current adjustment required when varying the current weighting coefficient (α) was determined with loudness balancing (2AFC). Finally, the pitch of a spanned channel was matched with the pitch of an intermediate physical electrode in a 2AFC procedure to assess the place of the spanned channel on the electrode array. RESULTS: : Spanning required significantly more current compensation to maintain equal loudness than current steering between adjacent electrode contacts. A significant decrease of discriminable intermediate pitches occurred with spanning in comparison with current steering between adjacent electrode contacts. No significant difference was found between the pitch-matched current steering coefficient and the theoretical coefficient corresponding a priori with the intermediate physical electrode. No significant difference was found between the data from the apical and the basal sections of the electrode array. CONCLUSIONS: : Spanning over wider electrode distance is feasible. With increasing electrode spanning distance, more current compensation is needed to maintain equal loudness, and a gradual deterioration in the just noticeable difference for pitch is observed. However, the pitch progression is linear. For a spanned signal with equal proportions of current delivered to both electrodes, pitch is equivalent to that produced by an intermediate physical electrode. |
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Authors:
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Jorien Snel-Bongers; Jeroen J Briaire; Filiep J Vanpoucke; Johan H M Frijns |
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Publication Detail:
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Type: Journal Article |
Journal Detail:
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Title: Ear and hearing Volume: 32 ISSN: 1538-4667 ISO Abbreviation: Ear Hear Publication Date: 2011 Mar-Apr |
Date Detail:
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Created Date: 2011-02-21 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 8005585 Medline TA: Ear Hear Country: United States |
Other Details:
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Languages: eng Pagination: 221-9 Citation Subset: IM |
Affiliation:
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1ENT-Department, Leiden University Medical Centre, Leiden, The Netherlands; and 2Advanced Bionics, European Auditory Research, Niel, Belgium. |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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