Fu Q J, Shannon R V
Department of Auditory Implants and Perception, House Ear Institute, Los Angeles, California 90057, USA.
Ear Hear. 1999 Aug;20(4):332-44. doi: 10.1097/00003446-199908000-00006.
This study was conducted to understand vowel recognition in cochlear implants as a function of the cochlear location and separation of the stimulated electrode pairs and as a function of the matching between speech spectral information and the location of the stimulated electrodes.
Four-electrode speech processors with a continuous interleaved sampling speech processing strategy were implemented through a custom interface in five subjects implanted with the Nucleus-22 cochlear implant. The temporal envelopes from four broad frequency bands were used to modulate 500 pps, 100 microsec/phase interleaved pulse trains delivered to four electrode pairs. Ten different frequency allocations and five sets of four-electrode configurations were tested. Each frequency allocation represented the same cochlear extent but different cochlear locations based on Greenwood's frequency-to-place formula. Recognition of multi-talker medial vowels was measured for each combination of parameters with no period of practice or adjustment.
Results showed that recognition of multi-talker vowels was highly dependent on frequency allocation for all electrode configurations. For a given electrode configuration maximum vowel recognition was observed with a specific frequency allocation. When the stimulated electrodes were shifted basally by 3 mm, the frequency allocation that produced the best performance also shifted basally by 3 mm. A similar pattern of vowel recognition was observed as a function of frequency allocation for electrode configurations that had the same apical-most electrode in each pair, regardless of location of the basal-most electrode in the pair. Subjects with different electrode insertion depths had similar trends in vowel recognition for each frequency allocation.
For a given electrode configuration, the best performance was obtained with processors with a specific frequency allocation. In addition, the apical-most member of each electrode pair had a much stronger influence on vowel recognition in electric hearing. Finally, results from this study also suggest that over time, patients with implants can partially adapt to a basal shift in place of stimulation.
本研究旨在了解人工耳蜗中的元音识别情况，它是耳蜗位置、受刺激电极对间距以及语音频谱信息与受刺激电极位置匹配情况的函数。
通过定制接口，对五名植入Nucleus-22人工耳蜗的受试者实施了采用连续交错采样语音处理策略的四电极语音处理器。来自四个宽频带的时间包络用于调制以500pps、100微秒/相位交错的脉冲序列，这些脉冲序列被输送到四个电极对。测试了十种不同的频率分配和五组四电极配置。根据格林伍德频率-位置公式，每种频率分配代表相同的耳蜗范围但不同的耳蜗位置。在没有练习或调整期的情况下，针对每种参数组合测量多说话者中间元音的识别情况。
结果表明，对于所有电极配置，多说话者元音的识别高度依赖于频率分配。对于给定的电极配置，在特定频率分配下观察到最大的元音识别率。当受刺激电极向基底方向移动3毫米时，产生最佳性能的频率分配也向基底方向移动3毫米。对于每对中最顶端电极相同的电极配置，无论该对中最底端电极的位置如何，观察到的元音识别模式类似。具有不同电极插入深度的受试者在每种频率分配下的元音识别趋势相似。
对于给定的电极配置，使用具有特定频率分配的处理器可获得最佳性能。此外，每个电极对中最顶端的电极对电听觉中的元音识别影响更大。最后，本研究结果还表明，随着时间的推移，植入患者可以部分适应刺激位置的基底移位。
