Language Control in the Bilingual BrainCrinion et al. (2006)

Amanda LeePSYC 260

Outline

Introduction Method Results Discussion Thoughts: Strengths and Limitations Summary

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

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

Introduction Hypothesis: reduced activation in the left anterior temporal

region when 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

Method Group 1: 11 German-English bilinguals PET

Group 2: 14 German-English bilingualsfMRI

Group 3: 10 Japanese-English bilinguals

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

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)

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

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

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

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

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

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?

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

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

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.

Thank you!

Questions?