Multilingual brain


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Multilingual brain

  1. 1. Multilingual BrainBy :Prakhar AsthanaEntry No.-2011CS1027Indian Institute of Technology Ropar, India
  2. 2. What is MultilingualismThere is no one definition.• People who speak or have been spoken in twoor more languages since birth.Or• People who have been speaking one languagesince birth and later learned other languages.Multilingual Brain 2
  3. 3. Types of Bilinguals• Compound Bilinguals: Has one semantic systembut two linguistic codes. Usually refers tosomeone whose two languages are learnt atsame time, often in same context.• Coordinate Bilinguals: Has two semantic systemsand two linguistic codes. Usually refers tosomeone whose two languages are learnt in twolanguages are learnt in distinctively separatecontexts• Subordinate bilingual: The weaker language isrepresented to the stronger language.Multilingual Brain 3
  4. 4. Mental lexicon of bilingualsMultilingual Brain 4
  5. 5. Hemispherical Lateralization ofLanguage• Involvement of one hemisphere of brain to aparticular activity makes it dominant• Language is believed to be heavily lateralizedfunction, with left hemisphere dominating theright one in handling language related tasksMultilingual Brain 5
  6. 6. • Left hemisphere controls lexical and syntacticlanguage, writing and speech, phonetics andsemantics.• It does not mean that right hemisphere servesno purpose.• Patients which get their right hemispheresurgically removed show no aphasia, but doshow deficiencies in verbal selection andmetaphor understanding.Multilingual Brain 6
  7. 7. How multilinguals switch betweenlanguages• Researchers have used brain imagingtechniques like functional magnetic resonanceimaging (fMRI) to investigate which brainregions are active when bilingual peopleperform tasks in which they are forced toalternate between their two languages.Multilingual Brain 7
  8. 8. • When bilinguals have to switch betweennaming pictures in Spanish and naming themin English, they show increased activation inthe :– dorsolateral prefrontal cortex (DLPFC )– anterior cingulate cortex (ACC)– bilateral supermarginal gyri– left inferior frontal gyrus (left-IFG)Multilingual Brain 8
  9. 9. • Patients with damage or lesion in these partsof brain undergo involuntary change inlanguage while speakingMultilingual Brain 9
  10. 10. How multilingual’s brain is different?• Are areas associated with L1 and L2 same ordifferent?• Is Multilingual’s brain structurally different?• What about brain activation?Multilingual Brain 10
  11. 11. • A major hypothesis: Different languages,different brain regions.• Studies conducted on bilingual aphasiacpatients show that in most of the cases onlyone of the mastered language is affected.• This gives an indirect proof to the abovementioned hypothesis.Multilingual Brain 11
  12. 12. • Eye tracking studies show that at early stagesof language acquisition both the languagesare parallely activated and have sharedcortical structures.Multilingual Brain 12
  13. 13. • fMRI scans show that for the late acquittedlanguages, language sensitive regions in thefrontal lobe of brain (Broca’s Area) arespatially separated from that of languagesensitive regions of native language• But when second language is acquired early,native and second language sensitive areastend to overlap.Multilingual Brain 13
  14. 14. • But in both late and early bilingual subjects,the temporal-lobe language-sensitive regions(Wernickes area) also show effectively little orno separation of activity based on the age oflanguage acquisition.Multilingual Brain 14
  15. 15. • fMRI scans show that there are also languagespecific zones in brain with L2-specific siteslocated exclusively in the posterior temporaland parietal lobes.• Bilinguals possessed seven perisylvianlanguage zones, which are L2 restricted.Multilingual Brain 15
  16. 16. Structural Changes in Bilingual’s Brain• Learning a second language increases thedensity of grey matter in the left anteriorparietal cortex• Age of second language acquisition andproficiency in that language affects its extent.Multilingual Brain 16
  17. 17. Structural Changes in Bilingual’s BrainMultilingual Brain 17
  18. 18. More brain activation in bilingualbrain• Cerebral Blood Flow(CBF) measuringtechniques show that in word repeating tasks,there is more blood flow in left putamen ofbrain for second languageMultilingual Brain 18
  19. 19. • Word generation has also led to larger foci ofbrain activation for the second languagewithin multilinguals.• Activation is principally found in the leftprefrontal cortex (inferior frontal, middlefrontal, and precentral gyri).Multilingual Brain 19
  20. 20. Effect of Age of Acquisition• The subcortical organization of languages inbilingual brain can change according to theage of acquisition of second language.Multilingual Brain 20
  21. 21. • Studies done on trilinguals show that moreneural substrates of Broca’s Area are engagedin performing same language tasks for lateracquired languages.• Language Activation follows order L3>L2>L1.• Later acquired languages require moreactivation.Multilingual Brain 21
  22. 22. Effect of Proficiency in Language• Researches show that very early bilingualsdisplay no difference in brain activation for L1and L2 — which is assumed to be due to highproficiency in both languages.• Larger cerebral activation is measured when alanguage is spoken less fluently than whenlanguages are spoken more fluently .Multilingual Brain 22
  23. 23. Effect of Proficiency in LanguageMultilingual Brain 23
  24. 24. Proficiency V Age of acquisition• Generally these go parallelly.• But what happens in contradictory case e.g.late proficient bilinguals.Multilingual Brain 24
  25. 25. Proficiency V Age of acquisition• Researches show that proficiency outweighsage of acquisition.• Cerebral representation is going to be samefor two languages if one is equally proficient inboth of them. It doesn’t matter when theywere acquired.Multilingual Brain 25
  26. 26. Bimodal Individuals• Bimodal individuals are those who are fluentin both sign language and oral language.• PET scans show that there is separate regionin the brain related to sign languageproduction and use.• Bimodal individuals use different areas of theright hemisphere depending on whether ifthey are speaking using verbal language orsign-language .Multilingual Brain 26
  27. 27. • fMRI scans show that bimodal bilinguals showgreater signal intensity in Wernicke’s areawhile using both languages in rapidalternation as compared to the oral and signlanguage monolinguals.Multilingual Brain 27
  28. 28. Advantages of being Multilingual• Bilinguals are more adept than monolingualsat solving certain kinds of mental puzzles.• Bilingual people are better than monolingualpeople at switching between two tasks.Multilingual Brain 28
  29. 29. • For e.g. when bilinguals have to switch fromcategorizing objects by color (red or green) tocategorizing them by shape (circle or triangle),they do so more rapidly than monolingualpeople.Multilingual Brain 29
  30. 30. Multilingual Brain 30
  31. 31. Bilingualism also help adults• Bilingualism’s effects also extend into thetwilight years.• Bilingual adults show delay in onset onalzeihmer’s disease by 4 years.Multilingual Brain 31
  32. 32. Multilingual Brain 32
  33. 33. If brain is an engine, bilingualismimproves its mileage• Actually brains of the bilingual peopleappeared to be in worse physical condition.• This suggest that despite of more braindamage, bilinguals were able to resist more.Multilingual Brain 33
  34. 34. Bilingualism- always a boon?• Researches gives evidence that bilingualchildren have less vocabulary in one languageas compared to monolinguals.• They take longer time and make more errorsin naming tasks.Multilingual Brain 34
  35. 35. Multilingual Brain 35
  36. 36. Questions Still Unanswered• Which proficiency level to be declared asbilingual/multilingual?• What is the best age at which one should startlearning second language?• Whether the two languages should be similar ordifferent to get more advantage?• Whether there is a limit to no. of languages uptowhich a person will always be in gain?• Whether there are any “better” languages thatshould be learnt?Multilingual Brain 36
  37. 37. Reference:• Fabbro, Franco. The neurolinguistics of bilingualism: An introduction.Psychology Pr, 1999.• Paradis, Michel. A neurolinguistic theory of bilingualism. Vol. 18. JohnBenjamins Publishing Company, 2004.• PERANI, D. (2001). The bilingual brain as revealed by functionalneuroimaging.Bilingualism: Language and cognition, 4(2), 179-190 .• Tierney, Michael C., et al. "PET evaluation of bilingual languagecompensation following early childhood brain damage." Neuropsychologia39.2 (2001): 114-121.• Kim, K. H., Relkin, N. R., Lee, K. -M., & Hirsch, J. (1997). Distinct corticalareas associated with native and second languages. Nature,388, 171–174.• Bialystok, E., Craik, F. I., & Luk, G. (2012). Bilingualism: Consequences formind and brain. Trends in Cognitive Sciences, 16(4), 240–250• Rönnberg, Jerker, Mary Rudner, and Martin Ingvar. "Neural correlates ofworking memory for sign language." Cognitive Brain Research 20.2 (2004):165-182.Multilingual Brain 37
  38. 38. Thank You