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Language Control in the Bilingual Brain

This overview examines the mechanisms of language control within the bilingual brain, focusing on a study that utilizes PET and fMRI to explore how bilingual individuals process languages. Key findings indicate that the left anterior temporal lobe operates independently of language while the left caudate nucleus serves as a language-dependent mechanism. The study highlights the role of semantic meaning in brain activation and emphasizes the need for future research to investigate broader linguistic diversity and its implications for language processing.

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Language Control in the Bilingual Brain

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  1. Crinionet al.(2006) Language Control in the Bilingual Brain Amanda Lee PSYC 260

  2. Outline • Introduction • Method • Results • Discussion • Thoughts: Strengths and Limitations • Summary

  3. Introduction • Multilingualism is a valuable asset and becoming more widespread • How does the bilingual brain use and process different languages? • Previous studies: both languages that a bilingual individual speaks activate the same brain areas: • Frontal, temporal and parietal regions

  4. Introduction • No specific areas determined for multilingualism • Left anterior temporal region highlighted in past research • Not confirmed to be responsible • Objective: identify language-dependent neuronal mechanisms to be tested on a semantic level

  5. Introduction • Hypothesis: reduced activation in the left anterior temporal regionwhen two semantically similar words are presented compared to a dissimilar pair. • Eg: trout-SALMON = less activation than trout-HORSE • Semantic priming effect • Both words in the pair also tested in different languages • Language-independent  neuronal responses the same throughout brain • i.e. trout-SALMON = less activation regardless of language • Only semantics affect brain activation • Language-dependent  different neuronal responses based on both semantics and language of target word

  6. Method • Group 1: 11 German-English bilinguals  PET • Group 2: 14 German-English bilinguals fMRI • Group 3: 10 Japanese-English bilinguals

  7. Method • 1750 ms long period • 250 ms to view prime word • Semantic decision based on physical characteristic • Baseline brain activation = deciding whether or not non-literary symbols were the same • Independent variables: congruency of the prime and target words in semantic relation and language • Dependent variables: Response time (s), accuracy (%), brain activation

  8. Results • All 3 groups: brain activation in frontal, temporal, parietal regions and visual cortices • Semantic priming evident in all cases • Response time for semantically related words (S) was 41 ms faster than unrelated words (U)

  9. Results • Reduced activation in left ventral anterior temporal lobe for semantically related word pairs • Same effect for both languages • Neural response only changed with semantic content (A) German-English fMRI. (B) Japanese-English fMRI. (C) German-English PET

  10. Results • Reduced activation in left caudate nucleus for semantically related words • Only if the prime and target words were the same language • Change accompanies language and semantics

  11. Discussion • Anterior temporal lobe  language-independent • Left caudate nucleus language-dependent • Works to extract the same semantic meaning from two different terms and make them equivalent

  12. Discussion • Possible neural mechanism of left caudate: • Same neurons respond to both languages • Increased neuronal firing when language input changes • Helps us modify output and use appropriate language

  13. Discussion • Damaged left caudate nucleus: • Impairs ability to respond to input change • Language production affected  switch languages inappropriately • Support for hypothesis and idea of general language-dependent structure • Not left anterior temporal lobe as thought • Left caudate projects to frontal, temporal, parietal lobes  thalamus  motor sequences for articulation

  14. Discussion: Further studies • Test wider variety of languages that are also more different from English • Tonal languages, different phonetics • Arrive at universal conclusion for language • Other aspects of language • Syntax, pragmatics, etc. • Study the left caudate • How does it connect to other brain structures to create a mechanism responsible for multilingualism?

  15. Thoughts: Strengths & Limitations • Strengths: • Thorough discussion on possible neuronal mechanisms for left caudate nucleus • Pinpointed specific structure and examined entire brain • Limitations • Not well laid out: data all in figure captions • Lack of detail  difficult to replicate experiment • Confusing 2 x 2 x 2 design: hard to track dependent variable • Ability to generalize results is questionable

  16. Summary • Left anterior temporal lobe is language-independent • only responds to semantic meaning • Left caudate nucleus plays a critical role in language control • activates upon change in semantic/language input • is the language-dependent mechanism for monitoring language • Future studies could test the proposed mechanism: left caudate and surrounding areas • broaden scope of languages tested to come to universal conclusion

  17. References • Crinion, J., Turner, R., Grogan, A., Hanakawa, T., Noppeney, U., Devlin, J.T., Aso, T., Urayama, S., Stockton, K., Usui, K., Green, D.W., Price, C.J. (2006). Language control in the bilingual brain. Science, 312 (5779), 1537-1540.

  18. Thank you! Questions?

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