Centre for Research on Brain, Language and Music, McGill University, Rabinovitch House, 3640 rue de la Montagne, Montreal, Quebec, H3G 2A8, Canada.
Chimei Medical Center, Taipei Medical University, Tainan, Taiwan.
Sci Rep. 2019 Jan 14;9(1):109. doi: 10.1038/s41598-018-36393-1.
In tonal languages, voice pitch inflections change the meaning of words, such that the brain processes pitch not merely as an acoustic characterization of sound but as semantic information. In normally-hearing (NH) adults, this linguistic pressure on pitch appears to sharpen its neural encoding and can lead to perceptual benefits, depending on the task relevance, potentially generalizing outside of the speech domain. In children, however, linguistic systems are still malleable, meaning that their encoding of voice pitch information might not receive as much neural specialization but might generalize more easily to ecologically irrelevant pitch contours. This would seem particularly true for early-deafened children wearing a cochlear implant (CI), who must exhibit great adaptability to unfamiliar sounds as their sense of pitch is severely degraded. Here, we provide the first demonstration of a tonal language benefit in dynamic pitch sensitivity among NH children (using both a sweep discrimination and labelling task) which extends partially to children with CI (i.e., in the labelling task only). Strong age effects suggest that sensitivity to pitch contours reaches adult-like levels early in tonal language speakers (possibly before 6 years of age) but continues to develop in non-tonal language speakers well into the teenage years. Overall, we conclude that language-dependent neuroplasticity can enhance behavioral sensitivity to dynamic pitch, even in extreme cases of auditory degradation, but it is most easily observable early in life.
在声调语言中,音高的变化会改变单词的意思,因此大脑不仅将音高视为声音的声学特征,还将其视为语义信息。在正常听力(NH)成年人中,这种对音高的语言压力似乎会使音高的神经编码更加敏锐,并根据任务的相关性产生感知上的益处,这种益处可能会扩展到言语领域之外。然而,在儿童中,语言系统仍然具有可塑性,这意味着他们对声音音高信息的编码可能不会得到太多的神经专门化,但可能更容易推广到与生态无关的音高轮廓。对于佩戴人工耳蜗(CI)的早期失聪儿童来说,这种情况似乎更为明显,因为他们的音高感严重受损,必须表现出对陌生声音的极大适应性。在这里,我们首次在 NH 儿童(使用扫频辨别和标签任务)中展示了声调语言对动态音高敏感性的优势,这种优势部分扩展到了 CI 儿童(即仅在标签任务中)。强烈的年龄效应表明,对音高轮廓的敏感性在声调语言使用者中很早就达到了成人水平(可能在 6 岁之前),但在非声调语言使用者中,这种敏感性仍在青少年时期不断发展。总的来说,我们得出的结论是,依赖语言的神经可塑性可以增强对动态音高的行为敏感性,即使在听觉严重受损的极端情况下也是如此,但在生命早期最容易观察到。