双语认知的功能性脑显像研究

Study of functional brain imaging for bilingual language cognition

双语和多语的大脑语言认知功能研究涉及语言神经表现，是一个跨学科的课题，需要神经解剖、神经功能、生物化学、精神和语言的不同水平的鉴别和区分。此外，特异的因素，如年龄、获得的方式和环境因素也影响神经表现。功能性脑显像，如PET、SPECT和功能性MRI可以探查双语受试者的语言神经表现，阐明大脑对双语认知的机制。功能性脑显像的研究显示，虽然两种语言的脑认知机制分享共同的成分，但与受试者母语比较，与第二语言有关的脑活性的类型不尽相同，表明两种不相关语言的词记忆处理既有共同的神经系统，也有不同的皮层区介导。不同的活性类型不仅与所使用的语言不同相关，也归因于获得的年龄或熟练水平，而达到熟练程度比获得的年龄更重要。PET研究显示，手语和口语似乎定位在同样的脑区，具有类似的局部脑血流类型；但手语还取决于空间信息，当健康正常的双语受试者用视觉方法感知手语时，功能解剖与既含有听觉又含有视觉成分的语言处理重叠。

Bilingual and muhilingual brain studies of language recognition is an interdisciplinary subject which needs to identify different levels involved in the neural representation of languages, such as neuroanatomical, neurofunctional, biochemical, psychological and linguistic levels. Furthermore, specific factors such as age, manner of acquisition and environmental factors seem to affect the neural representation. Functional brain imaging, such as PET, SPECT and functional MRI can explore the neurolinguisties representation of bilingualism in the brain in subjects, and elucidate the neuronal mechanisms of bilingual language processing. Functional imaging methods show differences in the pattern of cerebral activation associated with a second language compared with the subject＇s native language. It shows that verbal memory processing in two unrelated languages is mediated by a common neural system with some distinct cortical areas. The different patterns of activation differ according to the language used. It also could be ascribed either to age of acquisition or to proficiency level. And attained proficiency is more important than age of acquisition as a determinant of the cortical representation of the second language. The study used PET and SPECT shows that sign and spoken language seem to be localized in the same brain areas, and elicit similar regional cerebral blood flow patterns. But for sign language perception, the functional anatomy overlaps that of language processing contain both auditory and visual components. And the sign language is dependent on spatial information too.