1. 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

2. OBJECTIVE
BIG PICTURE GOAL
READ YOUR MIND
What you are thinking about
Which language you are thinking in
Whether you switched languages

3. BACKGROUND
BILINGUALISM 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

4. BACKGROUND
FMRI
fMRI provides both structural
and functional data
Gives brain activation per
voxel as a time series for
analyzable 4D data

5. BACKGROUND
MULTI-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

6. SUBJECTS
PROFESSORS AND FMRI OPERATORS
No ethics approval beforehand
3 volunteer subjects
Professors and fMRI Operators

7. EXPERIMENT
TASK DESIGN
!
+
!
ー
!
|
!
!
Axe
Japanese
Thought
English
Thought
!
!
Axe
English
Thought
Japanese
Thought
6s 1s 3s

8. EXPERIMENT
TRIAL
EXAMPLE TRIALS

9. EXAMPLE TRIAL 1
FIXATION
+
6s

10. EXAMPLE TRIAL 1
DIRECTION
ー
1s

11. EXAMPLE TRIAL 1
STIMULUS
Bear
3s

12. EXAMPLE TRIAL 2
FIXATION
+
6s

13. EXAMPLE TRIAL 2
DIRECTION
|
1s

14. EXAMPLE TRIAL 2
STIMULUS
熊
3s

15. ANALYSIS
MAIN 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.
EJ
EE
JE
JJ
Stimulus Language Switch Property Thought
GOAL: Differentiate between brain activation
for JJ, JE, EJ, and EE

16. ANALYSIS
OTHER CONTRASTS
Keep vs. Switch Language
Language Presented (J vs. E)
Language Thought (J vs. E)
Mammal vs. Tool Stimulus

17. RESULTS
CLASSIFICATION ACCURACY

18. RESULTS
SEARCHLIGHT DETECTED REGIONS

19. CONCLUSION
VALIDITY AND INTERPRETATION
Significant accuracy indicates underlying information
SEARCHLIGHT
Found regions corroborate past research
CLASSIFICATION ACCURACY
SIGNIFICANCE
First instance of simultaneously differentiating
between all contrasts in the same experiment

20. CONCLUSION
FUTURE WORK
Use fixation scans to perform resting-state fMRI

21. Thanks for Listening!
JUNE - AUGUST 2015
Special Thanks to:
赤間先生
TiROP
東京工業大学
Caltech