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)
Pag.27-4-2010 3Neurolinguistics, bilingualism and MRI
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)
Pag.27-4-2010 4Neurolinguistics, bilingualism and MRI
Studying the bilingual brain
-Norm rather than the exception
-Neuroplasticity (functional & physical changes)
-Education (training effects)
Pag.27-4-2010 5Neurolinguistics, bilingualism and MRI
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?
Pag.27-4-2010 6Neurolinguistics, bilingualism and MRI
1. question
-aphasiology: selective recovery of bilingual’s language skills
-Broca’s area only for native language?
-fMRI & PET
Pag.27-4-2010 7Neurolinguistics, bilingualism and MRI
Late vs. Early bilinguals (Kim et al., 1997)
Pag.27-4-2010 8Neurolinguistics, bilingualism and MRI
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)
Pag.27-4-2010 9Neurolinguistics, bilingualism and MRI
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)
Pag.27-4-2010 10Neurolinguistics, bilingualism and MRI
Convergence Hypothesis (Green, 2003)
-neural differences between native & L2 speakers may disappear as proficiency increases
-proficiency as predictor of neural representation
Pag.27-4-2010 11Neurolinguistics, bilingualism and MRI
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?
Pag.27-4-2010 12Neurolinguistics, bilingualism and MRI
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
Pag.27-4-2010 13Neurolinguistics, bilingualism and MRI
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
Pag.27-4-2010 14Neurolinguistics, bilingualism and MRI
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
Pag.27-4-2010 15Neurolinguistics, bilingualism and MRI
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?
Pag.27-4-2010 16Neurolinguistics, bilingualism and MRI
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
Pag.27-4-2010 17Neurolinguistics, bilingualism and MRI
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)
Pag.27-4-2010 18Neurolinguistics, bilingualism and MRI
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)
Pag.27-4-2010 19Neurolinguistics, bilingualism and MRI
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?
Pag.27-4-2010 20Neurolinguistics, bilingualism and MRI
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)
Pag.27-4-2010 21Neurolinguistics, bilingualism and MRI
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
Pag.27-4-2010 22Neurolinguistics, bilingualism and MRI
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)
Pag.27-4-2010 23Neurolinguistics, bilingualism and MRI
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)?
Pag.27-4-2010 24Neurolinguistics, bilingualism and MRI
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)
Pag.27-4-2010 25Neurolinguistics, bilingualism and MRI
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.
Pag.27-4-2010 28Neurolinguistics, bilingualism and MRI
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
Pag.27-4-2010 29Neurolinguistics, bilingualism and MRI
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?
Pag.27-4-2010 30Neurolinguistics, bilingualism and MRI
Corpus callosum variability (Coggins et al., 2003)
-bundle of axons connecting 2 cerebral hemispheres
-largest WM structure in the brain
Pag.27-4-2010 31Neurolinguistics, bilingualism and MRI
Structural differences
Table 1. Midsagittal corpus callosum regional area differences between
bilingual and monolingual individuals
Pag.27-4-2010 32Neurolinguistics, bilingualism and MRI
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?
Pag.27-4-2010 33Neurolinguistics, bilingualism and MRI
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?