Neural Basis of lan

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26 Οκτ 2013 (πριν από 3 χρόνια και 5 μήνες)

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Neural Basis of Language
and Set Shifting in
Bilinguals

Cesar Avila, Gabriele Garbin, Ana Sanjuan, Cristina
Forn, Juan
-
Carlos Bustamante, Aina Rodríguez
-
Pujadas, Mireia Hernández & Albert Costa

SUMMARY

-
Some reflections about Spanish
-
Catalan bilingualism


-

Language control in bilingualism


-

Study 1: Language control in Spanish
-
Catalan bilinguals


-

Task switching in bilinguals


-

Study 2: Task switching in Spanish
-
Catalan bilinguals and
monolinguals


-

Conclusions

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GENERAL PURPOSE

At least for some kind of early and
high proficient bilinguals, language
and cognitive switching would share
similar neural mechanisms.


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Spanish
-
Catalan Bilingualism: Some
reflections


Both languages are similar and easy to
learn simultaneously.


There are a lot of bilinguals, with a
diverse level of proficiency in Catalan.


Bilingualism developed because a person
lives in a regional context in which two
languages are co
-
official


There is often a concurrent L1 and L2
development since early infancy


Intense training in both languages



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A

good scenario for training executive functions
since infancy.

For example, one child can speak
or hear L1 or L2 as a function of a cue:


Catalan: father, grandparents (father), school,
some friends, some relatives....


Spanish: mother, grandparents (mother), at
kindergarten, some other friends, some other
relatives...


Plus zapping TV, reading, etc.


Involved in continous task switching....
Mixing
languages becomes effortless.


Spanish
-
Catalan Bilingualism:


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Special case of bilingualism where
switching may be trained since early
infancy


This implies that the
development of some executive functions
(response selection, response inhibition,
etc.) is intensively trained in parallel to
the development of language learning.


Special case for the development of a
“passive” bilingualism

A good
comprehension but low expression in L2
(See poster)


Spanish
-
Catalan Bilingualism: Some
reflections

BrainGlot 2009
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Barcelona

Objectives


To study the neural basis of language
control in Spanish
-
Catalan early bilinguals


To study the neural basis of task switching
in Spanish
-
Catalan early bilinguals when
compared with monolinguals


To test if both processes share the same
neural basis.

BrainGlot 2009
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Barcelona

Language control in early
bilinguals

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Barcelona

NEURAL BASIS OF LANGUAGE
CONTROL

Proposed by Abulatebi and Green,
2007

LIFG (Broca’s
area) and RIFG:
task switching
and language
control

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Barcelona

Abutalebi (2008)

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Behavioral Studies in language control

Picture Naming Task
(Costa & Santesteban, 2004)

Switching bewteen L1 and L2

L1=Spanish


Red pictures

L2=Catalan


Blue pictures

Non
-
Switch

Backward Switch

Backward

Switch

Non
-
Switch

Forward
-
Switch

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PREVIOUS BEHAVIORAL STUDIES

Asymmetrical
switching costs in low
proficient bilinguals:

-
Switching is slower
than non
-
switching

-
Naming in L1 from L2
is slower than naming
in L2 from L1.

-
Specific for late
bilinguals



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Barcelona

PREVIOUS BEHAVIORAL
STUDIES

Symmetrical switching
costs in early, high
proficient bilinguals:

-
Switching is slower
than non
-
switching

-
Naming in L1 is
slower than naming in
L2.

-
Specific for early
bilinguals
independently of
proficiency (for L3)



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Language control and lexical competition in bilinguals: an
event
-
related fMRI study. Neuroimage
Wang et al. (2007)


Participants


Twelve late bilingual students (6 females)
mean age 19.5 (from 18 to 21)









L1: Chinese



L2: English
learnt at 12.67(SD
+
1.2) years old
(poor proficiency score=3 over 5)

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Wang et al. (2007)

“English”



(200ms)

(200ms)

(2800 ms)

(2800 ms)

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Wang et al. (2007)

Forward switching
L1 to L2




Backward switching
L2 to L1




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Neural bases of asymmetric language switching
in second
-
language learners: An ER
-
fMRI study

(
Wang
et al.
, 2007)

Wang’s conclusion: the neural correlates of language
switching differ depending on the direction of the switch
and there does not seem to be a specific brain area
acting as a “language switch”.



But: 3 seconds of ITI is too long to investigate language
switching



Different types of bilingualism should be considered

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Language control and lexical competition in bilinguals: an
event
-
related fMRI study (Abutalebi et al., 2008)

Participants

12 late bilinguals (10 females). L1: German; L2:
French; AOA= 11.6.


fMRI

tasks

Simple

Naming

(SNc)
:

naming

pictures

in

L
1

Task

Selection

(TSc)
:

naming

pictures

or

generating

verbs

from

pictures

as

a

function

of

a

cue

(all

in

L
1
)


Language

Selection

(
LSc)
:

naming

pictures

in

L
1

or

L
2

as

a

function

of

a

cue

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Results I
(Abutalebi et al., 2008)

Abutalebi et al., 2008

Naming L1 in dual vs single task: LIFG,
SMA

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Results II
(Abutalebi et al., 2008)

Abutalebi et al., 2008

Naming L1 in bilingual vs monolingual task:
LIFG, RIFG, ACC, bilateral striatum

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Results III
(Abutalebi et al., 2008)

Abutalebi et al., 2008

Naming L1 in bilingual vs dual task: LIFG,
RIFG, ACC and left striatum

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Naming L2 vs L1 in bilingual context: LIFG,
RIFG, ACC and bilateral striatum

Results IV
(Abutalebi et al., 2008)

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Discussion


Results have confirmed Abutalebi and
Green’s model involving LIFG, RIFG, ACC
and the striatum in language control.


Directional changes from L1 to L2 and
vice
-
versa, were not considered.


Strange results: naming in L1 in bilingual
context overactivated the network more
than in a monolingual context, but less
than naming L2.

BrainGlot 2009
-

Barcelona

Language control and lexical competition in bilinguals: an
event
-
related fMRI study (Abutalebi et al., 2008)

Participants

12
early

bilinguals

(6
females
). L1:
Italian
; L2:
French
; AOA=
less

than

3. More
exposed

to

L2
than

to

L1


fMRI

task

Passively

listening

four

types

of

sentences
:

1.
Control
:

L
1


2.
Control
:

L
2

3.
Language

switch

from

L
1

to

L
2
.

4.
Language

switch

from

L
2

to

L
1
.


Switch vs non
-
switching activated the
LIFG, RIFG and bilateral superior temporal
gyrus.

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Results I
(Abutalebi et al., 2007)


Forward
switching into a
less dominant
language (L1)
activated the
left striatum and
ventral ACC


Backward
switching into a
dominant
language (L2)
did not activate
the language
control network

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Results II
(Abutalebi et al., 2008)

Discussion


Switching into a less dominant language
activated the language control network,
but not switching into a dominant
language.


This replicates Wang et al. study


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Study 1: Objective


To replicate Wang et al’s study in early
and high proficient bilinguals. Some
modifications were made:


ITI was 2 sec.


Performance was controlled: responses were
aloud


Cues and pictures were simultaneous
-

BrainGlot 2009
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Picture Naming Task

Participants:19 Spanish/Catalan early bilinguals.


-

7 males and 12 females


-

11 bilinguals learnt one language at home and the other at
the kindergarten, and each father speaks a different language
in 8 participants



-

High proficiency in both Spanish and Catalan.


-

All subjects were right
-
handed.


-

L1 and L2 were determined from infancy data: L1 was
Catalan for 11 and Spanish for 8.



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Task

Subjects were instructed to name simple pictures
in the correct language according to picture
colour (red, blue):


-

Forty
-
four pictures of common objects with
non
-
cognate names


-
Interstimuli interval: 2 seconds


-
Switch and non
-
switch trials


-
Responses were aloud.



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Naming sequence

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COMETA / MILOTXA, ESTEL

LAVADORA / RENTADORA

CERDO / PORC

MANZANA / POMA

PATO /
À
NEC

OJO / ULL

Task

There

were

240 trials:


-
120
switch

trials:

60
Spanish


Catalan

60 Catalan


Spanish



-
120
non
-
switch

trials: 60
Spanish


Spanish





60 Catalan


Catalan



An

examiner

inside

the

scanner

room

registered

responses




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Behavioral results.

Omissions and commission errors

Percentage of errors was
low.


There were no significant
differences between
languages in omission
errors, but differences in
commission errors
reached significance (p <
.05)

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General Switching

Brain

regions

involved

in

language

switching
.

The

comparison

switching

(L
1

L
2
,

L
2

L
1
)

vs
.

non

switching

(L
1

L
1
,

L
2

L
2
)

events

result

in

increased

activation

in

the

left

striatum

(
p

FWE
-
cor

<

.
05
)
.

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Forward and Backward Switching

Brain

regions

involved

in

forward

and

backward

language

switching
.

Activation

maps

of

forward

switching

(from

L
1

to

L
2
)

relative

to

L
2

non
-
switching

(red

cluster)

and

of

backward

switching

(from

L
2

to

L
1
)

relative

to

L
1

non
-
switching

(blue

cluster)
.


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Discussion



Language swtiching in early and high
proficient bilinguals activated the left
striatum


This structure
have been
involved in language selection and
switching.


Recent research has
specifically involved
the left striatum in detecting language
changes (Crinion et al., 2006; see Poster
Sanjuan et al).


No involvement of ACC and LIFG in
language swithing



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Discussion



When directional changes were studied:


Forward switching was associated with
the left striatum (as Abutalebi et al.,
2007).


Backward switching was associated with
the right striatum (see also Wang et al.,
2007; Abutalebi et al., 2008). Less is
known about the role of this area in
language selection.



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Cognitive control in early
bilinguals

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PREVIOUS BEHAVIORAL STUDIES


Several studies have evidenced that bilinguals
outperform monolinguals in non
-
linguistic
contexts requiring cognitive control, such as
Stroop
-
like tasks (e.g.
Bialystok & Martin, 2004;
Carlson & Meltzoff, 2008; Costa et al., 2008,
2009;
Hernández et al., 2009; Martin
-
Rhee &
Bialystok, 2008).




No previous neuroimaging studies


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PREVIOUS BEHAVIORAL STUDIES. (Costa et al.,
2008)

Used the ANT task to measure
activity in three different
attentional networks: alerting,
orienting and executive control.


Bilingual participants were faster
in performing the task


Bilinguals were more efficient in
the alerting and executive
control networks

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PREVIOUS BEHAVIORAL STUDIES. (Costa et al.,
2008)

They also studied switching costs
analyzing the sequence of trials:


Switching cost= C
-
I, I
-
C > C
-
C, I
-
I


Monolinguals suffered a greater
switching cost than bilinguals


This result has been also obtained
in children (
Bialystok &
Viswanathan, 2009
)

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Study 2: Objective


To investigate neural basis of task
switching in early and high proficient
bilinguals and monolinguals.



No previous studies on this topic, but task
swithcing has been associated with the
RIFG, the striatum and the ACC (Robbins,
2007).

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Participants

19 Spanish/Catalan
early bilinguals

-

11 bilinguals learnt one language at home and the
other in kindergarten, and in 8 each father speaks
a different language



-

High proficiency in both Spanish and Catalan.


-

All subjects were right
-
handed.


21 Spanish
monolinguals
: students from
monolingual regions just arrived to Castellon


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Task switching


-
Scanner: 1.5 T Siemens


Task: Subjects were asked to press one of two
buttons according to a combination of geometrical
pictures


CUES: SHAPE OR COLOR. Cues simultaneously
presented to pictures.


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Task switching

Task switching

COLOR

COLOR

COLOR

COLOR

SHAPE

SHAPE

SHAPE

SHAPE

Thumb
button

Index
Button

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Task switching

Conditions:

-
60 Non switch trials: Color
-
Color
or Shape
-
Shape

-
60 Switch trials: Color
-
Shape or
Shape
-
Color

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Behavioral results

Switch costs: 32 ms for monolinguals and 4ms for bilinguals (p=0.051)

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Switch costs: 4% for monolinguals and 0% for bilinguals (p < .05)

Behavioral results

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fMRI: Monolinguals

Increased activity in the left AAC and right IFG

fMRI: Bilinguals

Increased activity in the LIFG

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fMRI: Bilinguals vs. Monolinguals


Bilinguals>

Monolinguals
:

Increased

activation

in

the

left

inferior

frontal

gyrus

(IFG)

(blue

cluster)
.




Monolinguals>

Bilinguals
:

Increased

activation

in

the

right

IFG

(red

cluster)
.

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Performance correlates in bilinguals

Lower switching costs


Stronger activity in language control
areas (striatum and LIFG)

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Performance correlates in bilinguals

Higher switching costs


Stronger activity in task switching areas

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Conclusions

-

Monolinguals have shown significant switching costs and neural
activity in brain areas typically related to task switching: RIFG
and ACC.

-
Bilinguals have shown no switching costs and a neural activity in
brain areas typically related to language control: LIFG

-
Bilinguals seem to be an heterogeneous group: those with lower
switching costs activate the language control network (LIFG and
striatum), whereas those with higher switching costs activate as
monolinguals the rIFG.

The present results are consistent with the hypothesis
that
bilinguals' early training in mixing languages leads to the
involvement of language control brain areas when performing
non
-
linguistic cognitive tasks.

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General Conclusions


Language swtiching in bilinguals activates
brain areas involved in language control:
LIFG, RIFG, striatum and ACC.


Language control in early bilinguals is more
related to the striatum


Language control in late bilinguals is more
related to ACC.



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General Conclusions


Set
-
switching in monolinguals is related to
rIFG.


Set
-
switching in early, high proficient
bilinguals is related to the language
control network: LIFG and the striatum.


Early and high proficient bilinguals may
overlap brain areas involved the language
and cognitive switching


Future studies should serve to delimitate
which factor or factors are responsible for
these effects


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Thank You very much....


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