INVESTIGATING THE NEURAL BASIS OF TRIALWISE LANGUAGE SWITCHING IN LATE JAPANESE-ENGLISH BILINGUALS

VIBHOR KUMARヴ ィ ボ ー ク マ

ADVISOR: PROF. HIROYUKI AKAMA DEPARTMENT OF HUMAN SYSTEM SCIENCE

JUNE - AUGUST 2015

OBJECTIVEBIG PICTURE GOAL

READ YOUR MIND

What you are thinking about

Which language you are thinking in

Whether you switched languages

BACKGROUNDBILINGUALISM AND LANGUAGE SWITCHING

Bilingualism: The ability to think and communicate in two different languages

Language Switching: The process by which bilinguals switch languages

日本語 ENGLISH

BACKGROUNDFMRI

fMRI provides both structural and functional data

Gives brain activation per voxel as a time series for

analyzable 4D data

BACKGROUNDMULTI-VOXEL PATTERN ANALYSIS (MVPA)

MVPA: Using Machine Learning techniques to classify brain

activation at any point in time into different categories

SVM

GNB

Top Image from ”Svm max sep hyperplane with margin" by Cyc - Own work. Licensed under Public Domain via Commons - https://commons.wikimedia.org/wiki/File:Svm_max_sep_hyperplane_with_margin.png#/media/

File:Svm_max_sep_hyperplane_with_margin.png

SUBJECTSPROFESSORS AND FMRI OPERATORS

No ethics approval beforehand

3 volunteer subjects Professors and fMRI Operators

EXPERIMENTTASK DESIGN

!+

!ー

!|

!斧

!Axe

Japanese Thought

English Thought

!斧

!Axe

English Thought

Japanese Thought

6s 1s 3s

EXPERIMENTTRIAL

EXAMPLE TRIALS

EXAMPLE TRIAL 1FIXATION

+6s

EXAMPLE TRIAL 1DIRECTION

ー1s

EXAMPLE TRIAL 1STIMULUS

Bear3s

EXAMPLE TRIAL 2FIXATION

+6s

EXAMPLE TRIAL 2DIRECTION

|1s

EXAMPLE TRIAL 2STIMULUS

熊3s

ANALYSISMAIN CONTRAST

猫

Cat

一般的な愛玩動物の一種、気まぐれ

a small animal with four legs that people often

keep as a pet.

EJEE

JEJJ

Stimulus Language Switch Property Thought

GOAL: Differentiate between brain activation for JJ, JE, EJ, and EE

ANALYSISOTHER CONTRASTS

Keep vs. Switch Language

Language Presented (J vs. E)

Language Thought (J vs. E)

Mammal vs. Tool Stimulus

RESULTSCLASSIFICATION ACCURACY

RESULTSSEARCHLIGHT DETECTED REGIONS

CONCLUSIONVALIDITY AND INTERPRETATION

Significant accuracy indicates underlying information

SEARCHLIGHTFound regions corroborate past research

CLASSIFICATION ACCURACY

SIGNIFICANCEFirst instance of simultaneously differentiating between all contrasts in the same experiment

CONCLUSIONFUTURE WORK

Use fixation scans to perform resting-state fMRI

Thanks for Listening!

JUNE - AUGUST 2015

Special Thanks to:

赤間先生TiROP

東京工業大学Caltech