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Various aspects of multilingualism have been studied in the field of neurology. These include the representation of different language systems in the brain, the effects of multilingualism on the brain's structural plasticity, aphasia in multilingual individuals, and bimodal bilinguals (people who can speak one sign language and one oral language). Neurological studies of multilingualism are carried out with functional neuroimaging, and through observation of people who have suffered brain damage. The brain contains areas that are specialized to deal with language, located in the perisylvian cortex of the left hemisphere. These areas are crucial for performing language tasks, but they are not the only areas that are used; disparate parts of both right and left brain hemispheres are active during language production. In multilingual individuals, there is a great deal of similarity in the brain areas used for each of their languages. The little variation that there is depends on two main factors, age and language proficiency, with language proficiency being the most important. Multilingualism also affects the structural plasticity of the brain. Bilinguals, particularly those who learned their second language early in life, show increased density of grey matter in the inferior parietal cortex. Although there is some debate over whether this is due to genetic predisposition to increased density or to experience, overall the research suggests that the process of second-language acquisition restructures the brain itself. Insights into the neurology of multilingualism have been gained by the study of multilingual individuals with aphasia, or the loss of one or more languages as a result of brain damage. Bilingual aphasics can show several different patterns of recovery; they may recover one language but not another, they may recover both languages simultaneously, or they may involuntarily mix different languages during language production during the recovery period. These patterns are explained by the ''dynamic view'' of bilingual aphasia, which holds that the language system of representation and control is compromised as a result of brain damage. Research has also been carried out into the neurology of bimodal bilinguals, or people who can speak one oral language and one sign language. Work with PET scans shows that there is a separate area in the brain for working memory related to sign language, and that bimodal bilinguals use different areas in the right hemisphere depending on whether they are signing or speaking. Studies with bimodal bilinguals have also provided insight into the tip of the tongue phenomenon and into patterns of neural activity when recognizing facial expressions. ==Overview== Various aspects of multilingualism have been studied in the field of neuroscience. These include the representation of different language systems in the brain, the effects of multilingualism on the brain's structural plasticity, aphasia in multilingual individuals, and bimodal bilingualisms (people who can speak one sign language and one oral language). Neuroscientific studies of multilingualism are carried out with functional neuroimaging, electrophysiology, and through observation of people who have suffered brain damage. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Neuroscience of multilingualism」の詳細全文を読む スポンサード リンク
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