1) The document discusses the brain differences between monolingual and multilingual individuals. It describes various types of bilinguals and how their mental lexicons are organized. 2) Research shows that different languages may activate different brain regions, especially for later-acquired languages. Proficiency and age of acquisition also impact brain activation patterns. 3) Being multilingual provides cognitive advantages like improved task switching abilities. It may also delay the onset of Alzheimer's disease. However, multilingual children can have smaller vocabularies in individual languages initially.

1. Multilingual Brain
By :
Prakhar Asthana
Entry No.-2011CS1027
Indian Institute of Technology Ropar, India

2. What is Multilingualism
There is no one definition.
• People who speak or have been spoken in two
or more languages since birth.
Or
• People who have been speaking one language
since birth and later learned other languages.
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3. Types of Bilinguals
• Compound Bilinguals: Has one semantic system
but two linguistic codes. Usually refers to
someone whose two languages are learnt at
same time, often in same context.
• Coordinate Bilinguals: Has two semantic systems
and two linguistic codes. Usually refers to
someone whose two languages are learnt in two
languages are learnt in distinctively separate
contexts
• Subordinate bilingual: The weaker language is
represented to the stronger language.
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4. Mental lexicon of bilinguals
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5. Hemispherical Lateralization of
Language
• Involvement of one hemisphere of brain to a
particular activity makes it dominant
• Language is believed to be heavily lateralized
function, with left hemisphere dominating the
right one in handling language related tasks
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6. • Left hemisphere controls lexical and syntactic
language, writing and speech, phonetics and
semantics.
• It does not mean that right hemisphere serves
no purpose.
• Patients which get their right hemisphere
surgically removed show no aphasia, but do
show deficiencies in verbal selection and
metaphor understanding.
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7. How multilinguals switch between
languages
• Researchers have used brain imaging
techniques like functional magnetic resonance
imaging (fMRI) to investigate which brain
regions are active when bilingual people
perform tasks in which they are forced to
alternate between their two languages.
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8. • When bilinguals have to switch between
naming pictures in Spanish and naming them
in English, they show increased activation in
the :
– dorsolateral prefrontal cortex (DLPFC )
– anterior cingulate cortex (ACC)
– bilateral supermarginal gyri
– left inferior frontal gyrus (left-IFG)
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9. • Patients with damage or lesion in these parts
of brain undergo involuntary change in
language while speaking
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10. How multilingual’s brain is different?
• Are areas associated with L1 and L2 same or
different?
• Is Multilingual’s brain structurally different?
• What about brain activation?
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11. • A major hypothesis: Different languages,
different brain regions.
• Studies conducted on bilingual aphasiac
patients show that in most of the cases only
one of the mastered language is affected.
• This gives an indirect proof to the above
mentioned hypothesis.
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12. • Eye tracking studies show that at early stages
of language acquisition both the languages
are parallely activated and have shared
cortical structures.
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13. • fMRI scans show that for the late acquitted
languages, language sensitive regions in the
frontal lobe of brain (Broca’s Area) are
spatially separated from that of language
sensitive regions of native language
• But when second language is acquired early,
native and second language sensitive areas
tend to overlap.
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14. • But in both late and early bilingual subjects,
the temporal-lobe language-sensitive regions
(Wernicke's area) also show effectively little or
no separation of activity based on the age of
language acquisition.
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15. • fMRI scans show that there are also language
specific zones in brain with L2-specific sites
located exclusively in the posterior temporal
and parietal lobes.
• Bilinguals possessed seven perisylvian
language zones, which are L2 restricted.
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16. Structural Changes in Bilingual’s Brain
• Learning a second language increases the
density of grey matter in the left anterior
parietal cortex
• Age of second language acquisition and
proficiency in that language affects its extent.
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17. Structural Changes in Bilingual’s Brain
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18. More brain activation in bilingual
brain
• Cerebral Blood Flow(CBF) measuring
techniques show that in word repeating tasks,
there is more blood flow in left putamen of
brain for second language
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19. • Word generation has also led to larger foci of
brain activation for the second language
within multilinguals.
• Activation is principally found in the left
prefrontal cortex (inferior frontal, middle
frontal, and precentral gyri).
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20. Effect of Age of Acquisition
• The subcortical organization of languages in
bilingual brain can change according to the
age of acquisition of second language.
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21. • Studies done on trilinguals show that more
neural substrates of Broca’s Area are engaged
in performing same language tasks for later
acquired languages.
• Language Activation follows order L3>L2>L1.
• Later acquired languages require more
activation.
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22. Effect of Proficiency in Language
• Researches show that very early bilinguals
display no difference in brain activation for L1
and L2 — which is assumed to be due to high
proficiency in both languages.
• Larger cerebral activation is measured when a
language is spoken less fluently than when
languages are spoken more fluently .
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23. Effect of Proficiency in Language
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24. Proficiency V Age of acquisition
• Generally these go parallelly.
• But what happens in contradictory case e.g.
late proficient bilinguals.
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25. Proficiency V Age of acquisition
• Researches show that proficiency outweighs
age of acquisition.
• Cerebral representation is going to be same
for two languages if one is equally proficient in
both of them. It doesn’t matter when they
were acquired.
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26. Bimodal Individuals
• Bimodal individuals are those who are fluent
in both sign language and oral language.
• PET scans show that there is separate region
in the brain related to sign language
production and use.
• Bimodal individuals use different areas of the
right hemisphere depending on whether if
they are speaking using verbal language or
sign-language .
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27. • fMRI scans show that bimodal bilinguals show
greater signal intensity in Wernicke’s area
while using both languages in rapid
alternation as compared to the oral and sign
language monolinguals.
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28. Advantages of being Multilingual
• Bilinguals are more adept than monolinguals
at solving certain kinds of mental puzzles.
• Bilingual people are better than monolingual
people at switching between two tasks.
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29. • For e.g. when bilinguals have to switch from
categorizing objects by color (red or green) to
categorizing them by shape (circle or triangle),
they do so more rapidly than monolingual
people.
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30. Multilingual Brain 30

31. Bilingualism also help adults
• Bilingualism’s effects also extend into the
twilight years.
• Bilingual adults show delay in onset on
alzeihmer’s disease by 4 years.
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32. Multilingual Brain 32

33. If brain is an engine, bilingualism
improves its mileage
• Actually brains of the bilingual people
appeared to be in worse physical condition.
• This suggest that despite of more brain
damage, bilinguals were able to resist more.
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34. Bilingualism- always a boon?
• Researches gives evidence that bilingual
children have less vocabulary in one language
as compared to monolinguals.
• They take longer time and make more errors
in naming tasks.
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35. Multilingual Brain 35

36. Questions Still Unanswered
• Which proficiency level to be declared as
bilingual/multilingual?
• What is the best age at which one should start
learning second language?
• Whether the two languages should be similar or
different to get more advantage?
• Whether there is a limit to no. of languages upto
which a person will always be in gain?
• Whether there are any “better” languages that
should be learnt?
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37. Reference:
• Fabbro, Franco. The neurolinguistics of bilingualism: An introduction.
Psychology Pr, 1999.
• Paradis, Michel. A neurolinguistic theory of bilingualism. Vol. 18. John
Benjamins Publishing Company, 2004.
• PERANI, D. (2001). The bilingual brain as revealed by functional
neuroimaging.Bilingualism: Language and cognition, 4(2), 179-190 .
• Tierney, Michael C., et al. "PET evaluation of bilingual language
compensation following early childhood brain damage." Neuropsychologia
39.2 (2001): 114-121.
• Kim, K. H., Relkin, N. R., Lee, K. -M., & Hirsch, J. (1997). Distinct cortical
areas associated with native and second languages. Nature,388, 171–174.
• Bialystok, E., Craik, F. I., & Luk, G. (2012). Bilingualism: Consequences for
mind and brain. Trends in Cognitive Sciences, 16(4), 240–250
• Rönnberg, Jerker, Mary Rudner, and Martin Ingvar. "Neural correlates of
working memory for sign language." Cognitive Brain Research 20.2 (2004):
165-182.
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38. Thank You