母语为粤语的发育性阅读障碍儿童粤语-普通话-英语的语音加工缺陷脑机制

Whether the dysfunctional brain mechanisms of phonological processing deficits between mother language and the second language differ among children with developmental dyslexia (DD); whether these differences can be attributed to the differential writing systems between mother and the second language if there is any? These two related questions are always the hot topics of controversy in the world. Chinese, as a kind of ideographic writing system, plays an important role in research on brain mechanisms of bilingual phonological processing. In China, Cantonese and Mandarin are two kinds of important Chinese languages, which are significant different from each other and regarded as bilingualism. The Cantonese-speaking children will learn the second languages of Mandarin and English after they are enrolled into the primary school. Cantonese shares the same writing system with Mandarin, but it is completely different from English in writing system. These two features provide unique value for us to resolve the two questions above. In this study, we plan to select Cantonese-speaking children with DD, Mandarin-speaking children with DD, Cantonese-speaking children with normal reading, and Mandarin-speaking children with normal reading as participants to examine whether the differential writing systems across different languages plays an important role in the brain areas of bilingual phonological processing deficits in Chinese children with DD, and to explore the brain mechanisms of bilingual phonological processing deficits in Chinese children with DD by scanning all participants’ brain using fMRI technique. Our study had implications in selecting tailored interventions to Chinese children with DD, and in providing evidence to support the theory of bilingual phonological processing deficit.

发育性阅读障碍（DD）儿童母语与第二语言的语音加工缺陷脑机制是否不同；若不同是否由母语和第二语言间书写体系的差异所引起？这两个密切相关的问题一直是国际争论的热点。作为表意书写体系的汉语，在双语语音加工脑机制研究中具有重要价值。在中国，两种重要的汉语粤语和普通话差异显著，被视为双语。母语为粤语的儿童入学后学习第二语言普通话和英语。粤语的书写体系与普通话完全相同，与英语完全不同，这为我们解决上述两个问题提供了独特的素材。我们以粤语DD、普通话DD、粤语正常和普通话正常儿童为研究对象，利用fMRI技术，采用“Block Design”设计和静息态设计，通过对被试儿童粤-普-英的语音加工脑区定位和功能连接的两两比较，探索书写体系对汉语DD儿童双语语音加工缺陷脑机制的影响，揭示汉语DD儿童双语语音加工缺陷脑机制。本研究将为汉语DD儿童针对性矫治措施的建立，双语语音加工缺陷理论的完善提供依据。

作为表意书写体系的汉语，在双语语音加工脑机制研究中具有独特的价值。中国是一个多方言国家，其中粤语与普通话语音差异高达75%，被视为双语。粤语儿童入学后才开始学习普通话和英语。粤语的书写体系与普通话完全相同，与英语完全不同。但迄今为止，粤语人群在加工粤-普-英三语时大脑激活是否相同？与普通话人群比，粤语人群加工普通话是否不同？粤语人群独特语言经历是否会影响大脑的结构和功能？这些问题一直悬而未决。为解决上述问题，揭示书写体系对汉语人群的双语语音加工脑机制的影响，我们以粤语和普通话大学生为对象，采用功能磁共振（fMRI）的任务态、静息态、结构态和DTI对其脑功能和结构网络进行研究。结果发现：①在视觉和听觉语音加工任务中，粤语大学生粤语语音加工激活脑区与英语的更相似，而与普通话加工激活的脑区差别较大；粤语大学生加工普通话语音任务与加工粤语任务的脑激活模式的相似度为86.78%，与普通话大学生加工普通话语音任务的脑激活模式的相似度为99.27%。说明粤语人群加工普通话语音任务的脑激活模式与普通话母语者基本一致。②静息态fMRI结果显示，与普通话组比，粤语组在执行功能的带状-盖（CO）子网络有更强的功能连接，而默认网络和感觉运动网络的网络内功能连接强度弱；③DTI结果显示，与普通话组比，粤语组多个纤维束的MD和AD值增高，但FA值没有差异，说明双语经历使部分白质纤维束的轴突口径增加和髓鞘密度降低；④sMRI的T1像结果显示，与普通话组比，粤语组的右侧小脑灰质体积显著增大。上述结果说明，粤语人群独特的语言经历会塑造不同的大脑结构和功能网络，粤语人群更依赖于语音加工和执行控制脑网络的参与，而普通话人群更依赖于感知运动脑网络的参与。本研究揭示了汉语双语语音加工的脑机制，完善了双语加工理论，也为进一步揭示汉语发育性阅读障碍（DD）儿童母语与第二语言语音加工缺陷脑机制打下了坚实的基础。