Schatzer Reinhold, Vermeire Katrien, Visser Daniel, Krenmayr Andreas, Kals Mathias, Voormolen Maurits, Van de Heyning Paul, Zierhofer Clemens
Institute of Mechatronics, University of Innsbruck, Technikerstrasse 25, 6020 Innsbruck, Austria.
C. Doppler Laboratory for Active Implantable Systems, Institute of Ion Physics and Applied Physics, University of Innsbruck, Technikerstrasse 25, 6020 Innsbruck, Austria.
Hear Res. 2014 Mar;309:26-35. doi: 10.1016/j.heares.2013.11.003. Epub 2013 Nov 16.
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° to 758°. 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 (-0.16 octaves re. Greenwood) and the mean shifts in the basal (<240°; -0.33 octaves) and middle (-0.35 octaves) regions were statistically significant, the shift in the apical region (>480°; 0.26 octaves) was not. Standard deviations of frequency-place functions were approximately half an octave at electrode insertion angles below 480°, 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 Hz and 450 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 Hz to 300 Hz only on electrodes at angular insertion depths beyond 360°, 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.
八名非植入耳听力接近正常的人工耳蜗使用者比较了分别呈现给双耳的脉动电刺激和纯音声刺激的音高感知。六名受试者植入了31毫米的MED-EL FLEX(SOFT)电极，两名受试者植入了24毫米的中等(M)电极，最顶端触点的插入角度范围为565°至758°。在第一个实验中，频率-位置函数是通过将纯音与呈现给各个电极的1500pps未调制脉冲序列进行匹配而得出的，并与沿着柯蒂氏器的格林伍德频率位置图进行比较。虽然所获得的频率-位置函数的总体中位数向下偏移(-0.16倍频程，相对于格林伍德)以及基底(<240°；-0.33倍频程)和中部(-0.35倍频程)区域的平均偏移具有统计学意义，但顶端区域(>480°；0.26倍频程)的偏移没有统计学意义。在电极插入角度低于480°时，频率-位置函数的标准差约为半个倍频程，在较高角度位置增加到一个倍频程，而各个函数逐渐趋于平稳。在第二个实验中，受试者将呈现给阵列顶端半部各个电极的未调制脉冲序列的速率与100赫兹至450赫兹的低频纯音进行匹配。目的是研究电极位置对时间音高线索显著性的影响，用于通过对选定顶端通道的速率调制来呈现时间精细结构信息的编码策略。大多数受试者仅在角度插入深度超过360°的电极上实现了与100赫兹至300赫兹音调频率的可靠匹配，而与450赫兹音调的速率匹配主要在较浅插入角度的电极上实现。仅对于第二圈中的电极，速率-音高函数的平均斜率与纯音参考值没有显著差异，这表明它们可用于在时间精细结构刺激策略中通过速率调制对通道内精细频率信息进行编码。
