Electric-acoustic pitch comparisons in single-sided-deaf cochlear implant users: Frequency-place functions and rate pitch

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• 作者：Reinhold Schatzer ; Katrien Vermeire ; Daniel Visser ; Andreas Krenmayr ; Mathias Kals ; Maurits Voormolen ; Paul Van de Heyning ; Clemens Zierhofer
• 关键词：CI ; cochlear implant ; RIB ; research interface box ; 2I-2AFC ; two-interval two-alternative forced choice ; pps ; pulses per second ; PSE ; point of subjective equality ; PTA ; pure-tone average ; SE ; standard error of the mean
• 刊名：Hearing Research
• 出版年：March, 2014
• 年：2014
• 卷：309
• 期：Complete
• 页码：26-35
• 全文大小：1127 K

文摘

Eight cochlear implant users with near-normal hearing in their non-implanted ear compared pitch percepts for pulsatile electric and acoustic pure-tone stimuli presented to the two ears. Six subjects were implanted with a 31-mm MED-EL FLEX^SOFT electrode, and two with a 24-mm medium (M) electrode, with insertion angles of the most apical contacts ranging from 565掳 to 758掳. In the first experiment, frequency-place functions were derived from pure-tone matches to 1500-pps unmodulated pulse trains presented to individual electrodes and compared to Greenwood's frequency position map along the organ of Corti. While the overall median downward shift of the obtained frequency-place functions (鈭?.16 octaves re. Greenwood) and the mean shifts in the basal (<240掳;聽鈭?.33 octaves) and middle (鈭?.35 octaves) regions were statistically significant, the shift in the apical region (>480掳; 0.26 octaves) was not. Standard deviations of frequency-place functions were approximately half an octave at electrode insertion angles below 480掳, increasing to an octave at higher angular locations while individual functions were gradually leveling off.

In a second experiment, subjects matched the rates of unmodulated pulse trains presented to individual electrodes in the apical half of the array to low-frequency pure tones between 100聽Hz and 450聽Hz. The aim was to investigate the influence of electrode place on the salience of temporal pitch cues, for coding strategies that present temporal fine structure information via rate modulations on select apical channels. Most subjects achieved reliable matches to tone frequencies from 100聽Hz to 300聽Hz only on electrodes at angular insertion depths beyond 360掳, while rate-matches to 450-Hz tones were primarily achieved on electrodes at shallower insertion angles. Only for electrodes in the second turn the average slopes of rate-pitch functions did not differ significantly from the pure-tone references, suggesting their use for the encoding of within-channel fine frequency information via rate modulations in temporal fine structure stimulation strategies.