McGill University, Montreal, Canada.
Colorado State University, Fort Collins, CO, USA.
Sci Rep. 2024 Sep 30;14(1):22595. doi: 10.1038/s41598-024-73320-z.
For individuals with hearing loss, even successful speech communication comes at a cost. Cochlear implants transmit degraded information, specifically for voice pitch, which demands extra and sustained listening effort. The current study hypothesized that abnormal pitch patterns contribute to the additional listening effort, even in non-tonal language native speaking normally hearing listeners. We manipulated the fundamental frequency (F0) within and across words, while participants listen and repeat (simple intelligibility task), or listen, repeat, and later recall (concurrent encoding task) the words. In both experiments, the F0 manipulations resulted in small changes in intelligibility but no difference in free recall or subjective effort ratings. Pupillary metrics were yet sensitive to these manipulations: pupil dilations were larger when words were monotonized (flat contour) or inverted (the natural contour flipped upside-down), and larger when successive words were organized into a melodic pattern. The most likely interpretation is that the natural or expected F0 contour of a word contributes to its identity and facilitate its matching and retrieval from the phonological representation stored in long-term memory. Consequently, degrading words' F0 contour can result in extra listening effort. Our results call for solutions to improve pitch saliency and naturalness in future development of cochlear implants' signal processing strategies, even for non-tonal languages.
对于听力损失的个体来说，即使成功地进行了言语交流，也需要付出代价。人工耳蜗植入物传输的信息质量较差，特别是在语音音高方面，这需要额外的、持续的听力努力。本研究假设，即使是在母语为非声调语言的正常听力者中，异常的音高模式也会导致额外的听力努力。我们在参与者听和重复（简单理解任务）或听、重复，然后回忆（同时编码任务）单词时，在词内和词间操纵基频（F0）。在这两个实验中，F0 操纵导致可理解性略有变化，但自由回忆或主观努力评分没有差异。瞳孔测量指标对这些操纵仍然敏感：当单词单调化（平坦轮廓）或倒置（自然轮廓颠倒）时，瞳孔扩张较大，当连续的单词组织成旋律模式时，瞳孔扩张更大。最有可能的解释是，单词的自然或预期 F0 轮廓有助于其身份识别，并有助于从长期记忆中存储的语音表示中匹配和检索它。因此，降低单词 F0 轮廓会导致额外的听力努力。我们的结果呼吁在未来开发人工耳蜗植入物的信号处理策略时，即使对于非声调语言，也要解决提高音高显著性和自然度的问题。
