Magnetic Resonance Imaging study in bilinguals

摘要

Asubstantialproportion of theworldpopulationspeakmorethanonelanguage. Overthepastfewyears, a plethora ofMagnetic Resonance Imaging (MRI) studies has been performed to identify the neural correlates of bilingual processing. Broca's areaandWernicke's areaare the two most important areas for language processingin the brain.Many theories exist about the processing of first language (L1)and second language (L2) in bilinguals. FunctionalMRI (fMRI)studiesbased on blood oxygen level dependent (BOLD) signal changeshave been a sensitive tool in brain mapping.With the help of fMRI,a brainregionresponsibleforaparticularlanguagefunctioningcanberecognized.Images of the brain are acquired during an activity or stimulus and compared with at-rest images. Despiteanimpressivepsycholinguistic efforttoexplorethewayinwhichmorethan one languageisrepresented andprocessed, controversysurroundsboth issues. fMRIStudieshave reporteda common neuralrepresentation of language forearly-acquisition,fluentbilinguals, whereas a dissociated representation of L1 and L2 forlate-acquisition, nonfluentbilinguals. ThemainlimitationsoffMRIarelack ofspatialresolutionandperhapsthedifferencesthatwe arepursuingarenotcodedinspacebutratherintime.Other techniques such as Diffusion Tensor Imaging (DTI) and Diffusion Weighted Imaging (DWI) are also used in bilingual research.DTInon-invasively tracks the nerve fibers using the information of directional diffusion of water in white matter.Using DTI, higher white matter (WM) integrity was seen in healthy older bilinguals which inturn sustains the cognitive performance. DWI fiber tracking method suggests that the brain structure and function have close relationship.DWI can demonstrate the probable structure and organization of Broca’s area-basal ganglia loops. Future developments in the neurolinguistic research using a combination of modalities along with various clinical studiesin aphasia patients willenhanceour knowledgeregardinglanguage representationin thebilingualbrainand also provide potential opportunities for bilingual aphasia therapy.

目录

封面

声明

DECLARATION

CERTIFICATE

ABBREVIATIONS

目录

英文摘要

Introduction

1.Mechanism of language processing

1.1 Neural structures in language processing

1.2 Alphabeticandlogographiclanguagesystems

1.3Structural MRI \(Voxel-basedmorphometry\)

2. Functional Magnetic Resonance Imaging \(fMRI\)

2.1Principles of BOLD

2.2. Evidence towards shared neural system in fMRI \(BOLD\) studies

2. 3 Evidence towards differentiated neural system in fMRI \(BOLD\) studies

2.4Reasons fordiscrepanciesinfMRI \(BOLD\) studies

2.5 Limitations of fMRI based on BOLD signal changes

3. Diffusion Tensor Imaging\(DTI\)

4. Diffusion-weightedimaging\(DWI\)

5. Bilingual aphasia

6.Language conflict in bilinguals

7.Future prospects in bilingual research and treatment of bilingual aphasia

Summary

致谢

参考文献

Literature Review

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