Department of Communication Sciences and Disorders, College of Behavioral and Community Sciences, University of South Florida, Tampa, FL 33620-8100, USA.
Ear Hear. 2011 Mar-Apr;32(2):238-50. doi: 10.1097/AUD.0b013e3181fb8390.
Previous studies have confirmed that current steering can increase the number of discriminable pitches available to many cochlear implant (CI) users; however, the ability to perceive additional pitches has not been linked to improved speech perception. The primary goals of this study were to determine (1) whether adult CI users can achieve higher levels of spectral cue transmission with a speech processing strategy that implements current steering (Fidelity120) than with a predecessor strategy (HiRes) and, if so, (2) whether the magnitude of improvement can be predicted from individual differences in place-pitch sensitivity. A secondary goal was to determine whether Fidelity120 supports higher levels of speech recognition in noise than HiRes.
A within-subjects repeated measures design evaluated speech perception performance with Fidelity120 relative to HiRes in 10 adult CI users. Subjects used the novel strategy (either HiRes or Fidelity120) for 8 wks during the main study; a subset of five subjects used Fidelity120 for three additional months after the main study. Speech perception was assessed for the spectral cues related to vowel F1 frequency, vowel F2 frequency, and consonant place of articulation; overall transmitted information for vowels and consonants; and sentence recognition in noise. Place-pitch sensitivity was measured for electrode pairs in the apical, middle, and basal regions of the implanted array using a psychophysical pitch-ranking task.
With one exception, there was no effect of strategy (HiRes versus Fidelity120) on the speech measures tested, either during the main study (N = 10) or after extended use of Fidelity120 (N = 5). The exception was a small but significant advantage for HiRes over Fidelity120 for consonant perception during the main study. Examination of individual subjects' data revealed that 3 of 10 subjects demonstrated improved perception of one or more spectral cues with Fidelity120 relative to HiRes after 8 wks or longer experience with Fidelity120. Another three subjects exhibited initial decrements in spectral cue perception with Fidelity120 at the 8-wk time point; however, evidence from one subject suggested that such decrements may resolve with additional experience. Place-pitch thresholds were inversely related to improvements in vowel F2 frequency perception with Fidelity120 relative to HiRes. However, no relationship was observed between place-pitch thresholds and the other spectral measures (vowel F1 frequency or consonant place of articulation).
Findings suggest that Fidelity120 supports small improvements in the perception of spectral speech cues in some Advanced Bionics CI users; however, many users show no clear benefit. Benefits are more likely to occur for vowel spectral cues (related to F1 and F2 frequency) than for consonant spectral cues (related to place of articulation). There was an inconsistent relationship between place-pitch sensitivity and improvements in spectral cue perception with Fidelity120 relative to HiRes. This may partly reflect the small number of sites at which place-pitch thresholds were measured. Contrary to some previous reports, there was no clear evidence that Fidelity120 supports improved sentence recognition in noise.
先前的研究已经证实，当前的转向可以增加许多人工耳蜗（CI）用户可分辨的音高数量；然而，感知额外音高的能力并未与语音感知的改善相关联。本研究的主要目标是确定（1）成人 CI 用户是否可以使用实现当前转向（Fidelity120）的语音处理策略比使用先前的策略（HiRes）获得更高水平的频谱线索传输，并且，如果是这样，（2）可以从个体差异中的音高位置敏感性来预测改善的幅度。次要目标是确定 Fidelity120 是否支持比 HiRes 更高水平的噪声中的语音识别。
一项在体重复测量设计评估了 10 名成人 CI 用户在使用 Fidelity120 相对于 HiRes 的语音感知性能。在主要研究期间，受试者使用新策略（HiRes 或 Fidelity120）8 周；其中 5 名受试者在主要研究之后又使用了 Fidelity120 3 个月。使用与元音 F1 频率、元音 F2 频率和辅音发音位置相关的频谱线索评估语音感知；元音和辅音的整体传输信息；以及噪声中的句子识别。使用心理物理音高排序任务在植入阵列的顶端、中间和底部区域测量电极对的音高位置敏感性。
除了一项例外，在测试的语音测量中，无论是在主要研究（N=10）期间还是在 Fidelity120 的扩展使用后（N=5），策略（HiRes 与 Fidelity120）都没有影响。例外是在主要研究期间，HiRes 相对于 Fidelity120 在辅音感知方面具有较小但显著的优势。对个体受试者数据的检查表明，在使用 Fidelity120 8 周或更长时间后，10 名受试者中有 3 名受试者相对于 HiRes 表现出对一个或多个频谱线索的感知改善。另外 3 名受试者在 8 周的时间点表现出对 Fidelity120 中频谱线索感知的初始下降；然而，来自一名受试者的证据表明，这种下降可能会随着更多的经验而得到解决。音高位置阈值与 Fidelity120 相对于 HiRes 对元音 F2 频率感知的改善呈反比。然而，在其他频谱测量（元音 F1 频率或辅音发音位置）中没有观察到音高位置阈值与其他频谱测量之间的关系。
研究结果表明，在一些 Advanced Bionics CI 用户中，Fidelity120 支持对频谱语音线索感知的微小改善；然而，许多用户没有明显的益处。对于元音频谱线索（与 F1 和 F2 频率相关）的感知改善比辅音频谱线索（与发音位置相关）更有可能发生。在 Fidelity120 相对于 HiRes 的频谱线索感知改善方面，音高位置敏感性与改善之间的关系不一致。这可能部分反映了测量音高位置阈值的站点数量较少。与一些先前的报告相反，没有明确的证据表明 Fidelity120 支持噪声中的句子识别改善。
