Bilingualism/Multilingualism to Protect Against Cognitive ...
From Neurolinguistics Of Bilingualism to Cognitive Control
Transcript of From Neurolinguistics Of Bilingualism to Cognitive Control
From Neurolinguistics Of Bilingualism to Cognitive Control
Esli Struys, MuRe, CLIN, Vrije Universiteit Brussel
Campus Jette, 27 April 2010
Pag.27-4-2010 2Neurolinguistics, bilingualism and MRI
Broca & Wernicke revisited
-perisylvian language areas
-Broca: IFG -Wernicke: STG
-Broca’s patients under MRI (Dronkers et al., 2007)
-speaking still possible without Broca’s area (Plaza et al., 2009)
-Broca plays critical role in cognitive control (Koechlin & Jubault, 2003)
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4 Branches of Neurolinguistics
-Aphasiology & dyslexia (language pathology)
-Localization of language processing (MRI & PET)
-Time course of language processing (EEG & MEG)
-Language Acquisition (L1 & L2) (interdisciplinary)
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Studying the bilingual brain
-Norm rather than the exception
-Neuroplasticity (functional & physical changes)
-Education (training effects)
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Research questions
1. Does a bilingual speaker represent each language in different areas of the brain?
2. What are the neural correlates of language switching?
3. Which variables affect neural representation of 1. & 2.?
4. Effect on other cognitive skills?
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1. question
-aphasiology: selective recovery of bilingual’s language skills
-Broca’s area only for native language?
-fMRI & PET
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Late vs. Early bilinguals (Kim et al., 1997)
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Parallel lexical activity
-parallel activation of 2 languages in –word production (Kroll et al., 2008)
–word recognition (Van Hell & De Groot, 2008)
-morphological strategies (Portin et al., 2008)
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Syntactical activity in L1 & L2
-fundamentally different (Ullman, 2001; Clahsen & Felser, 2006) or integrated?
-cross-linguistic priming effects (Hartsuiker & Pickering, 2008)
-syntactic violations & ambiguities (Kotz et al., 2008)
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Convergence Hypothesis (Green, 2003)
-neural differences between native & L2 speakers may disappear as proficiency increases
-proficiency as predictor of neural representation
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Then why selective recovery?
-networks involved in representation language components distinct from circuits involved in control of such networks (Green, 2005)
-training effects (proficiency) related to the latter?
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The role of development
Comparable
proficiency L1 &
L2 reached
(balanced
bilingualism)
Differential activity for
L2
(i) In same L1-related
prefrontal networks
but engaged to
larger extent
(ii) Areas more
anterior to classical
language areas,
related to cognitive
control
Parallel activity L1 & L2
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2. question
DLPFC (BA 9, 46) � during language switching in picture naming (Hernandez et al., 2000)
� highly fluent bil. show increase of DLPFC activity in « bilingual mode »
� neurological « signature » for bilingualism
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3. question
-Age of Acquisition (AoA)– Early Bilinguals (Sim)
– Early-late Bilinguals (Seq).
-Manner of Acquisition– Implict vs. Explicit learning (unexplored)
-Proficiency (LEAP-Q, BAT)– Balanced vs. unbalanced
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Role of AoA
-late L2 learners recruit more neural resources (Golestani et al., 2006)
-increase in LIFG activity for late learners (Hernandez et al., 2007)
-critical period for grammatical processing?
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4. question
-advantages in metalinguistic skills (Cummins, 1978)
-disadvantages in lexical access– Corrected for if vocabulary size is taken into account (Bialystok et al., 2008)
– Compensated for by improved executive functioning?
-similar developmental pattern (Werker et al., 2008)
-delays onset of aging
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Our research
-Centre for Linguistics
-Multilingual Research Unit–SLA
–Bi- and multilingualism
–Bilingual education–Positive effects on calculation scores (Comblain & Rondal, 1993; Jäppinen, 2005)
–STIMOB (Van de Craen et al., 2005)
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Additive Bilingualism(Baetens Beardsmore, 1986)
-opposite to « semilingualism » or subtractive bilingualism
-increased metalinguistic awareness (Cummins, 1978; Cromdal, 1999)
-creativity (Kessler & Quinn, 1988) & cognitive flexibility (Kovacs & Mehler, 2009)
- knowledge of 2 languages « greater than the sum of the parts » (Hakuta & Bialystok, 1994)
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Going beyond the language domain
-competition between lexical & grammatical activation in L1 & L2 (Green, 1998)
-solved by inhibiting any active, non-target language
-effect on non-linguistic skills, like cognitive control (or selective attention), arithmetic?
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Bilingualism, Executive Functioning & Number
-bilinguals show clear advantages for executive control (Green, 1998; Bialystok et al., 2009)
-neurocognitive advantages for bilinguals in a selective attention task(Mondt, 2007)
-inhibitory control as a predictor of individual children’s mathematical ability (Bull & Scerif, 2001)– Lesion studies show possible link with arithmetic (Zamarian et al., 2006)
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Research Setup
-Dependent variable– Brain activity during an arithmetic verification task as registered with fMRI (Hôpital Erasme, ULB, Anderlecht)
-Independent variable(s)– Mono- vs. Bilingualism (linguistic background)
– School- vs. Non-school language (educational background)
-Population of 31 children
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Mental Calculation Paradigm (Menon et al., 2000)
-originally designed to dissociate prefrontal and parietal activation
-control condition– 5-digit chain (press if « zero »)
-two experimental conditions
– 3-operand equations (x + y = z)
– 4-operand equations (x + y = z – a)
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Conclusions
-s-l bilinguals: least number of active brain regions, left lateralized brain activity
-n-s-l bilinguals and monolinguals: similar patterns of additional bilateral activity in frontal and subcortical areas
-no intraparietal activity (HIPS or AG) in children during arithmetic verification
-results indicate – a training effect (s-l bil vs. n-s-l bil)– an advantage for bilinguals (s-l bil vs. mono)?
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Bilingualism & Simon task
-does bilingualism enhance nonverbal control processes?– Arithmetic facts still phonologically stored
-differential brain-behavior relations (Bialystok et al., 2005)– Fast responses in bilinguals related to left hem. regions bordering language areas
-executive functions boosted in children? (Bialystok et al., 2007)
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Attention Network Task (Costa et al., 2008)
-early & balanced bilingualism aids conflict resolution
-ANT taps into 3 different nonverbal attentional mechanisms– Alerting
– Orienting
– Executive control
Pag.
Pag.
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Why Simon & Stroop task?
-different types of conflict–Stimulus-reponse (Simon) versus stimulus-stimulus (Stroop)
–Conflict at stage of response selection (Simon) versus conflict at stage of stimulus identification (Stroop)
Green Red BluePurple Blue Purple 2 7 9 4
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Differences in GM density (VBM)
-increased GM density in E-I bil. in left inferior parietal cortex (Mechelli et al., 2004)
-modulated by AoA & Prof.
-correspondence with verbal fluency?
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Corpus callosum variability (Coggins et al., 2003)
-bundle of axons connecting 2 cerebral hemispheres
-largest WM structure in the brain
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Structural differences
Table 1. Midsagittal corpus callosum regional area differences between
bilingual and monolingual individuals
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Conclusions CC study
-CC undergoes adaptation to accommodate multiple language faculty
-difference due to increase in fibre numbers emanating from L hem to R hem?
-relationship with AoA & proficiency?
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Conclusion
-different languages � same neural representations (AoA, Prof)
-how to avoid interference?
-selective attention to relevant language, suppression of other
-effect on cognitive control
-structural changes?