Acoustic to electric pitch comparisons in cochlear implant subjects with residual hearing

Article Article scientifique Article Acoustic to electric pitch comparisons in cochlear implant subjects with residual hearing eng 2006-02-01 2006-06 author Boex Colette 0000-0002-9374-4791 28086 author Baud Lionel 134872 author Cosendai Grégoire 100516 author Sigrist Alain 763272 author Kos Izabel 105443 author Pelizzone Marco 26345 110-124 10.1007/s10162-005-0027-2 16450213 1438-7573 PMC2504582 The aim of this study was to assess the frequency-position function resulting from electric stimulation of electrodes in cochlear implant subjects with significant residual hearing in their nonimplanted ear. Six cochlear implant users compared the pitch of the auditory sensation produced by stimulation of an intracochlear electrode to the pitch of acoustic pure tones presented to their contralateral nonimplanted ear. Subjects were implanted with different Clarion electrode arrays, designed to lie close to the inner wall of the cochlea. High-resolution radiographs were used to determine the electrode positions in the cochlea. Four out of six subjects presented electrode insertions deeper than 450 degrees . We used a two-interval (one acoustic, one electric), two-alternative forced choice protocol (2I-2AFC), asking the subject to indicate which stimulus sounded the highest in pitch. Pure tones were used as acoustic stimuli. Electric stimuli consisted of trains of biphasic pulses presented at relatively high rates [higher than 700 pulses per second (pps)]. First, all electric stimuli were balanced in loudness across electrodes. Second, acoustic pure tones, chosen to approximate roughly the pitch sensation produced by each electrode, were balanced in loudness to electric stimuli. When electrode insertion lengths were used to describe electrode positions, the pitch sensations produced by electric stimulation were found to be more than two octaves lower than predicted by Greenwood's frequency-position function. When insertion angles were used to describe electrode positions, the pitch sensations were found about one octave lower than the frequency-position function of a normal ear. The difference found between both descriptions is because of the fact that these electrode arrays were designed to lie close to the modiolus. As a consequence, the site of excitation produced at the level of the organ of Corti corresponds to a longer length than the electrode insertion length, which is used in Greenwood's function. Although exact measurements of the round window position as well as the length of the cochlea could explain the remaining one octave difference found when insertion angles were used, physiological phenomena (e.g., stimulation of the spiral ganglion cells) could also create this difference. From these data, analysis filters could be determined in sound coding strategies to match the pitch percepts elicited by electrode stimulation. This step might be of main importance for music perception and for the fitting of bilateral cochlear implants. Acoustic Stimulation Aged Cochlea / diagnostic imaging Cochlear Implantation / instrumentation Cochlear Implants / standards Electric Stimulation Electrodes, Implanted Hearing / physiology Humans Middle Aged Pitch Discrimination / physiology Radiography Dewey 616.8 FNRS 32-56352.99 FNRS 31-68263.02 61 Département des neurosciences cliniques 226 false Journal of the Association for Research in Otolaryngology 7 2 6a38b77a-574e-4d13-ac32-0cf472f53a89 Article (Published version) Restricted Article-scientifique-from-europePmc.pdf 1246614 application/pdf CC BY restrictedAccess Faculté de médecine / Section de médecine clinique / Département des neurosciences cliniques

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Acoustic to electric pitch comparisons in cochlear implant subjects with residual hearing	Journal of the Association for Research in Otolaryngology			2006	150	0

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