Multilingual brain

The Multilingual Brain This report discusses the neuroscientific and social aspect of the Multilingual Brain. It discusses how language is stored in brain, how multilingual brain is different from monolingual brain, how multilinguals use language, advantages and disadvantages of being a multilingual etc. Since most of the research which is done regarding multilingualism is done on bilingual individuals, Multilingual/Bilingual have been used invariably throughout this report without distinguishing between them and they both refer to same thing unless mentioned otherwise

2013

Prakhar Asthana Entry No:2011CS1027

3/29/2013

The Multilingual Brain

2 | P a g e

1. Who is Bilingual? According to current linguistic, psychological, and neurolinguistic approaches,

the term ‘‘bilingual’’ refers to all those people who use two or more languages

or dialects in their everyday lives (Grosjean 1994). In this report, dialects are

subsumed under the term ‘‘language.’’

2. Types of Bilinguals Though bilingualism may be classified according to the pairing up of the

languages spoken, Weinreich (1963) discussed three types bilingualism in

terms of the ways in which it was thought that the concepts of a language

were encoded in the individual’s brain (Romaine, 1995). These are:

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.

Following figure illustrates mental lexicon of all types of bilinguals


3 | P a g e

3. Hemispherical Lateralization of

Language It refers to the distinction between

functions of the right and the left

hemispheres of the brain. Involvement of

one hemisphere of brain to a particular

activity makes it dominant[1]. Language is

believed to be heavily lateralized function,

with left hemisphere dominating the right

one in handling language related tasks. It is

suggested that that language lateralization

depends on handedness, sex,

multilingualism, sign-language and also vary

among cultures.

It is been found out that it is left hemisphere that controls lexical and syntactic

language, writing and speech[2], phonetics and semantics. Split-brain studies

present evidence that, despite the right hemisphere having no “speech”, one is

still able to understand language through the auditory system. It does not

mean that right hemisphere serves no purpose. Patients which undergo

hemispherectomy to get their right hemisphere surgically removed show no

aphasia, but do show deficiencies in verbal selection and metaphor

understanding.


4 | P a g e

4. 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. For instance, when bilingual people have to switch

between naming pictures in Spanish and naming them in English, they show

increased activation in the dorsolateral prefrontal cortex (DLPFC), a brain

region associated with cognitive skills like attention and inhibition[3]Along with

the DLPFC, language switching has been found to involve such structures as the

anterior cingulate cortex (ACC), bilateral supermarginal gyri, and left inferior

frontal gyrus (left-IFG), regions that are also involved in cognitive control.[4] The

left-IFG in particular, often considered the language production center of the

brain, appears to be involved in both linguistic and non-linguistic cognitive

control. Other than this, Semantic priming techniques show that the left caudate is also

responsible for switching from one language to another. Patients with damage

or lesion in this part of brain undergo involuntary change in language while

speaking.[5]

5. How multilingual brain is different? One of the most interesting questions in Neurolinguistics is the representation

of language in bilingual and the multilingual subjects. A fundamental issue is

whether the cerebral representation in the bi- and multilinguals differ from

that of monolinguals, and if so, in which specific way. This is an

interdisciplinary question which needs to identify and differentiate different

levels involved in the neural representation of languages, such as

neuroanatomical, neurofunctional, biochemical, psychological and linguistic

levels.

Do multilingual speakers use different areas of brain for different language? Or

same part of brain is used. A major hypothesis is that in individuals speaking


5 | P a g e

two or more languages the different languages are represented and processed

in distinct brain regions. Studies conducted on bilingual aphasiac patients show

that in most of the cases only one of the mastered language is affected.[6]This

gives an indirect proof to the above mentioned hypothesis.

I. Distinct/Shared areas associated with native and

second languages The ability to acquire and use several languages selectively is a unique and

essential human capacity.

Eye tracking studies show that at early stages of language acquisition both

the languages are parallely activated and have shared cortical structures [7]

but 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.

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.[8]

However it does not mean that, first and second languages have all the

regions of brain in common. 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, in which L2 sites were significantly

underrepresented when compared with the distribution of language sites in

monolinguals. These L2-restricted zones overlapped the primary language

areas found in monolingual children, indicating that these zones become

dedicated to L1 processing.[9]

II. Structural Plasticity of bilingual brain It is found out that age of second language acquisition and proficiency in

that language affects the grey matter density of the brain[10] learning a


6 | P a g e

second language increases the density of grey matter in the left anterior

parietal cortex and it is modulated by the proficiency attained and the age

of acquisition


7 | P a g e

III. More brain activation in bilingual brain Putamen is a round structure

located at the base of the forebrain

According to the PET scan [11] Left

putamen plays a significant role in

articulation of second language L2

(learned after the age of 5 years).

Cerebral Blood Flow (CBF) was

measured and only significant

change that was observed while

repeating words in first and second language (L1 and L2) was increased

CBF in the left putamen when words in L2 language were articulated.

Role of putamen in articulation is supported by the fact that Foreign

Accent Syndrome (FAS) in which patients develop what appears to be a

foreign accent can occur after left putaminal damage.

Word generation (phonemic verbal fluency) has also led to larger foci of

brain activation for the least fluent language(s) within multilinguals

(observed using fMRI). Regardless of language, however, activation is

principally found in the left prefrontal cortex (inferior frontal, middle

frontal, and precentral gyri). Additionally, activation can be observed in

the supplementary motor area and parietal lobe. [12]

6. Effect of Age of Acquisition It is suggested that the first language might have more subcortical

representation than the second language and the subcortical organization of

languages in bilingual brain can change according to the age of acquisition of

second language.

It is also found that The age of second language acquisition determines the

variability in activation elicited by narration in three languages in Broca's and


8 | P a g e

Wernicke's area.[13]Studies done on trilinguals show that more neural

substrates are engaged in performing same language tasks for later acquired

languages[14]. This activation is larger for L3 than L2 and L1, and less for L1 than

for L2. Familiarity with a language reduces the brain activation required for its

use

7. Effect of Proficiency in Language Functional neuroimaging research has shown 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. Additionally, in highly proficient late

bilinguals, there is a common neural network that plays an important role in

language production tasks[15] whereas, in less proficient late bilinguals,

spatially separated regions are activated in Broca's area for L1 and L2[8] Finally,

it has been found that larger cerebral activation is measured when a language

is spoken less fluently than when languages are spoken more fluently [16]


9 | P a g e

8. But which matters more- Proficiency or Age of

Acquisition? Does individuals which have learned second language at a later stage of their

life but have mastered it upto the level of excellence tends to have same or

different cerebral representation as compared to individuals who learnt

second language early in their life? In other words is cerebral representation of

early bilinguals is same as late proficient bilinguals? Or more specifically if two

persons have same proficiency level in second language do they tend to have

same or different representation of languages in their brain even if their age of


10 | P a g e

acquisition of second language is different? Does proficiency is more

preferable criteria than age of acquisition as compared to age of acquisition?

Researches show that proficiency outweighs age of acquisition. In bilinguals,

achieved proficiency, and possibly language exposure, are more crucial than

age of acquisition in the cerebral representation of languages[17]. 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.

9. Bimodal Individuals Bimodal individuals are those who are fluent in both sign language and oral

language. Neuroscientific research on Bimodal individuals has been carried

out. The effect of this experience on the brain compared to brain regions in

monolinguals or bilinguals has only recently become a research interest. It is

now used to provide insight on syntactic integration and language control of

bilinguals[18]. PET scans from these studies show that there is separate region

in the brain for working memory related to sign language production and use.

These studies also find that Bimodal individuals use different areas of the right

hemisphere depending on whether if they are speaking using verbal language

or gesticulating using sign-language [19].

PET scans of a sign language bilingual (English and American Sign Language)

male with left frontal lobe damage revealed that there is an increased right

hemisphere activity compared to normal controls during spontaneous

generation of narrative in both English and American Sign Language (ASL).[20]

fMRI scans show that showing sign language to deaf and hearing-abled signers

(one who know sign language) and showing written English to hearing non-

signers activates the classical language areas of the left hemisphere in both

cases[21]

fNIR scans comparing brain activity of bimodal bilinguals with those of oral

language and sign language monolinguals in picture naming tasks has been

done. These scans show that bimodal bilinguals show greater signal intensity


11 | P a g e

in Wernicke’s area while using both languages in rapid alternation as

compared to the oral and sign language monolinguals [22].

10. Bilingual Aphasia Bilingual aphasia is a specific form of aphasia which affects one or more

languages of a bilingual (or multilingual) individual. An abundance of insight

about language storage in the brain comes from studying bilingual/ mulilingual

individuals afflicted with a form of aphasia.

The symptoms and severity of aphasia in bilinguals/ mulitlinguals depend on

how many languages the individual knows, what order they have them stored

in the brain, how frequently they use each one, how proficient they are in

using those languages and patient's levels of education and literacy.[24]

I. Theories of assessing bilingual aphasia There are two proposed theoretical views generally taken to approach

bilingual aphasia[37].

Localizationist View

Dynamic View

a) Localizationist View It is the traditional view of assessing bilingual aphasia. This approach

views different languages as stored in different regions of the brain;

therefore, is the reason why bilingual/ multilingual aphasics may lose

one language they know, but not the other(s).[25]

b) Dynamic View

This approach proposes that the language system of representation and control is compromised as a result of damage.[26] The dynamical theory approach suggests that the language system is supervised by a dynamic equilibrium between the existing language capabilities and the constant alteration and adaptation to the communicative requirements of the environment.[31][32] This theory is supported by the functional imaging data of normal bilinguals and holds that fluency in a language is lost because of an increase in the activation threshold. The Dynamic view


12 | P a g e

offers an explanation for selective recovery of language and many reported recovery patterns in bilingual aphasia [26]

II. Recovery from bilingual aphasia The concept of different recovery patterns was first noted by Albert

Pitres in 1895. Since then, seven patterns have been outlined[26]:

a) Differential recovery

It occurs when there is greater inhibition of one language than of

another. Recovery of L1 is more common than L2 in this recovery

mode [28].

b) Selective recovery In this one language remains impaired and the other recovers; the

activation threshold for the impaired language is permanently

increased.

c) Parallel recovery It occurs when both impaired languages improve to a similar extent

and concurrently.

d) Successive recovery In this complete recovery of one language precedes the recovery of

the other.

e) Alternating recovery In this the language that was first recovered will be lost again due to

the recovery of the language that was not first recovered.

f) Alternating antagonistic recovery It occurs when the language that was not used for a time becomes

the currently used language i.e. on one day the patient is able to

speak in one language while the next day only in the other.


13 | P a g e

g) Blended recovery There is a pathological mixing of two languages i.e. the elements of

the two languages are involuntarily mixed during language

production.

Research that compares the prevalence of the different recovery patterns

generally shows that the most common pattern of recovery is parallel

recovery, followed by differential, blended, selective, and successive.[23]

In 1977, it was proposed that the recovery pattern of a bilingual aphasic

can be properly predicted if the effects of age, proficiency, context of

acquisition, and type of bilingualism are known in combined.[29] It has

recently been reported that language status (how frequently the language

is used in comparison to other languages), lesion type or site, the context in

which the languages were used, the type of aphasia, and the manner in

which the language could not reliably predict recovery patterns.[30]

11. Advantages of bi/multi-lingualism

Studies show that the speed with which multilingual subjects perform

tasks, with-and-without mediation required to resolve language-use

conflict, is better in bilingual than monolingual subjects[40]. Bilingual people

are also better than monolingual people at switching between two tasks;

for example, 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, [33] reflecting better cognitive

control when changing strategies on the fly.


14 | P a g e

The cognitive and neurological benefits of bilingualism also extend into older

adulthood. Bilingualism appears to provide a means of fending off a natural

decline of cognitive function and maintaining what is called “cognitive

reserve.”[4] Cognitive reserve refers to the efficient utilization of brain networks to

enhance brain function during aging. Bilingual experience may contribute to this

reserve by keeping the cognitive mechanisms sharp and helping to recruit

alternate brain networks to compensate for those that become damaged during

aging. Older bilingual people enjoy improved memory and executive

control relative to older monolingual people, which can lead to real-world health

benefits.

Bilingualism also helps during ageing. A recent study shows that being bilingual

can delay the onset of Alzheimer’s disease by about 4 years[34].


15 | P a g e

In the subsequent study researches found out that bilingual test subjects’ brains

were more damaged as compared to monolingual test subjects’. But even then

they were able to resist Alzheimer’s disease for longer period. If the brain is an

engine, bilingualism may help to improve its mileage, allowing it to go farther on

the same amount of fuel.

12. Bilingualism – Always a boon? Are there any disadvantages that are associated with being bilingual? Researches

show that bilinguals are slow at retrieving common words. They take longer time

and make more errors in naming tasks[39]. This is so because their attention is

divided across multiple languages. It is found out that bilingual children have less

vocabulary in one language as compared to monolinguals [35].


16 | P a g e

13. Questions still unanswered Though a lot of study is being done in this area but still there are some

questions whose answers are yet to be found like

• 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?

Further studies are needed to elucidate the neuronal mechanisms of

bi/multilingual language processing. A promising perspective for future

bi/multilingual research is an integrative approach using brain imaging studies

with a high spatial resolution such as fMRI, combined with techniques with a

high temporal resolution, such as magnetoencephalography (MEG).


17 | P a g e

14. References: 1. Bear, M. F., Connors, B. W., Paradiso, M. A. (2007). Neuroscience: Exploring the Brain, 3rd edition.

Lippincott Williams & Wilkins: USA

2. Purves, D., Augustine, G. J., Fitzpatrick, D., Hall, W. C., LaMantia, A., McNamara, J. O., White, L. E.

(2008). Neuroscience, 4th edition. Sinauer Associates, Inc.: Massachusetts, USA

3. Hernandez, A. E., Martinez, A., & Kohnert, K. (2000). In search of the language switch: An fMRI study of

picture naming in Spanish-English bilinguals. Brain and Language, 73(3), 421–431.]

4. Bialystok, E., Craik, F. I., & Luk, G. (2012). Bilingualism: Consequences for mind and brain. Trends in

Cognitive Sciences, 16(4), 240–250

5. Crinion, Jenny, et al. "Language control in the bilingual brain." Science312.5779 (2006): 1537-1540.

6. Paradis, M (1989) .Bilingual Aphasia Test. New Jersey: Lawrence Erlbaum Associates, Inc.

7. Marian, Viorica, Michael Spivey, and Joy Hirsch. "Shared and separate systems in bilingual language

processing: Converging evidence from eyetracking and brain imaging." Brain and language 86.1 (2003):

70-82.

8. 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.

9. Lucas, Timothy H., Guy M. McKhann, and George A. Ojemann. "Functional separation of languages in the

bilingual brain: a comparison of electrical stimulation language mapping in 25 bilingual patients and 117

monolingual control patients." Journal of neurosurgery 101.3 (2004): 449-457

10. Mechelli, A., Crinion, J. T., Noppeney, U., O'Doherty, J., Ashburner, J., Frackowiak, R. S., & Price, C. J.

(2004). Neurolinguistics: Structural plasticity in the bilingual brain.Nature, 431(7010), 757.

11. Klein, D., Zatorre, R. J., Milner, B., Meyer, E., & Evans, A. C. (1994). Left putaminal activation when

speaking a second language: evidence from PET.Neuroreport, 5(17), 2295-2297.

12. Yetkin, O., Yetkin, F. Z., Haughton, V. M., & Cox, R. W. (1996). Use of functional MR to map language in

multilingual volunteers. American Journal of Neuroradiology, 17(3), 473-477.

13. Bloch, Constantine, et al. "The age of second language acquisition determines the variability in activation

elicited by narration in three languages in Broca’s and Wernicke’s area." Neuropsychologia 47.3 (2009):

625-633.

14. Vingerhoets, Guy, et al. "Multilingualism: an fMRI study." Neuroimage 20.4 (2003): 2181-2196.

15. Chee, M. W., Tan, E. W., & Thiel, T. (1999). Mandarin and English single word processing studied with

functional magnetic resonance imaging. The Journal of Neuroscience, 19(8), 3050-3056.

16. Yetkin, Oguz, et al. "Use of functional MR to map language in multilingual volunteers." American Journal

of Neuroradiology 17.3 (1996): 473-477.

17. PERANI, D. (2001). The bilingual brain as revealed by functional neuroimaging.Bilingualism: Language and

cognition, 4(2), 179-190

18. Pyers, Jennie E., and Karen Emmorey. "The Face of Bimodal Bilingualism Grammatical Markers in

American Sign Language Are Produced When Bilinguals Speak to English Monolinguals." Psychological

science 19.6 (2008): 531-535.

19. Rönnberg, Jerker, Mary Rudner, and Martin Ingvar. "Neural correlates of working memory for sign

language." Cognitive Brain Research 20.2 (2004): 165-182.

20. Tierney, Michael C., et al. "PET evaluation of bilingual language compensation following early childhood

brain damage." Neuropsychologia 39.2 (2001): 114-121.


18 | P a g e

21. Neville, Helen J., et al. "Cerebral organization for language in deaf and hearing subjects: biological

constraints and effects of experience." Proceedings of the National Academy of Sciences 95.3 (1998): 922-

929.

22. Kovelman, Ioulia, et al. "Dual language use in sign-speech bimodal bilinguals: fNIRS brain-imaging

evidence." Brain and language 109.2 (2009): 112-123..

23. Paradis, Michel. "Bilingual and polyglot aphasia." Handbook of neuropsychology 3 (2001): 69-91.

24. Connor, Lisa Tabor, et al. "Effect of socioeconomic status on aphasia severity and recovery." Brain and

language 78.2 (2001): 254-257.

25. Albert, Martin L., Loraine K. Obler, and Albert Obler. The bilingual brain: Neuropsychological and

neurolinguistic aspects of bilingualism. New York: Academic Press, 1978..

26. Paradis, Michel. "The other side of language: Pragmatic competence." Journal of Neurolinguistics 11.1

(1998): 1-10.Stemmer, Brigitte, and Harry A. Whitaker. Handbook of neurolinguistics. Academic Press,

1998.

27. Paradis, Michel. A neurolinguistic theory of bilingualism. Vol. 18. John Benjamins Publishing Company,

2004.

28. Fabbro, Franco. The neurolinguistics of bilingualism: An introduction. Psychology Pr, 1999.

29. Paradis, Michel. "Bilingualism and aphasia." Studies in neurolinguistics 3 (1977): 65-121.

30. Fabbro, Franco. "The bilingual brain: Bilingual aphasia." Brain and Language79.2 (2001): 201-210.

31. De Bot, Kees, Wander Lowie, and Marjolijn Verspoor. "A dynamic systems theory approach to second

language acquisition." Bilingualism language and cognition 10.1 (2007): 7.

32. Wanner, Anja. "Review: Applied Linguistics; Language Acquisition: Verspoor et al. (2011)". Retrieved 13

November 2012.

33. Prior, A., & MacWhinney, B. (2010). A bilingual advantage in task switching. Bilingualism: Language and

Cognition, 13(2), 253–262.

34. Schweizer, T. A., Ware, J., Fischer, C. E., Craik, F. I., & Bialystok, E. (2012). Bilingualism as a contributor to

cognitive reserve: Evidence from brain atrophy in Alzheimer's disease. Cortex, 48(8), 991–996.

35. PEETS, KATHLEEN F., and SUJIN YANG. "Receptive vocabulary differences in monolingual and bilingual

children." Bilingualism: Language and Cognition 13.4 (2010): 525-531

36. http://www.brad.ac.uk/staff/pkkornakov/bilHermeneus2000.htm

37. http://en.wikipedia.org/wiki/Multilingualism

38. http://www.nytimes.com/2011/05/31/science/31conversation.html

39. http://www.researchgate.net/post/What_is_Multilingualism_How_is_it_useful_or_harmful_for_students

40. http://www.dana.org/news/cerebrum/detail.aspx?id=39638

http://linguistlist.org/issues/22/22-4013.html

Education

Multilingual brain