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27-11-2012 1Neurolinguistics of bilingualism
Neurolinguistics of Bilingualism
Linguistics & Neurosciences, 6th Class
Nov 13th, 2012
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Neurolinguistics of bilingualism
3 parts
-Recovery patterns of bilingual aphasia (13/11)
-L1 & L2 representation inbilingual brains (13/11)
-Effects on cognition (27/11)
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Neurolinguistics of bilingualism
Further planning
-22/11: WOT Olga Kepinska
-4/12: guest lecture by Elke De Witte (PhD Research Fellow at VUB/FWO)
–A neurolinguistic approach to the management of supratentorial tumors –
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Neurolinguistics of bilingualism
Neurolinguistics
-What is the study object?
–Neurolinguistics studies the cognitive processes underlying language processing
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Neurolinguistics of bilingualism
Principles
-Traditional language testing tells us very little about the cognitive processes that underlie language processing.
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Neurolinguistics of bilingualism
Principles
-Language processing in the brain shares many cognitive processes with other cognitive domains.
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Neurolinguistics of bilingualism
Principles
-Implicit acquisition of language leads to recruitment of similar cognitive mechanisms as explicit acquisition with higher learning gains.
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Neurolinguistics of bilingualism
Principles
-If proficiency is similar, younger learners always show more efficient language processing in the brain.
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Neurolinguistics of bilingualism
Research questions
-Where & when are languages represented in the multilingual brain?
-What are the variables that affect thislocalization and timing of language processing?
-What regions are involved in themanagement or control of the differentlanguages?– What is the effect on other forms of cognitive control?
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Neurolinguistics of bilingualism
Terminological confusion
-What different types ofbilingualism do you know?–AoA: early, late, adult L2;
–simultaneous vs. sequentials (or: L2 learners);
–Proficiency: balanced, L1 or L2 dominant
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Neurolinguistics of bilingualism
Recovery patterns in aphasia
-What will determine recovery after bilingual aphasia?–Pitre’s Law: most familiar language
–Ribot’s Law: L1
–Minskowki’s Law: language with strongest emotional association
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Neurolinguistics of bilingualism
Recovery patterns in aphasia
A is a 35-year old Danish sailor, who has been working on ships travelling between many parts of the world. After a stroke, he fluctuates between Danish, English, Spanish, and German and mixes all 4 languages.
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Neurolinguistics of bilingualism
Recovery patterns in aphasia
B is a retired German professor of Sanskrit. In the acute stage after a stroke, he is diagnosed having Wernicke’s aphasia. When he is asked to read aloud, he utters only Sanskrit or Sanskrit-like words.
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Neurolinguistics of bilingualism
Recovery patterns in aphasia
C was born in Italy and moved to the United States when he was 12 years old. At age 55, he suffers from a stroke and, at first, speaks only Italian (which he has not used since he was a child). He receives language therapy in English and gradually recovers most of his English. Then, however, he can no longer speak Italian.
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Neurolinguistics of bilingualism
Dissociated recovery
-Parallel recovery
-Differential recovery
-Selective recovery
-Mixed recovery
-Successive recovery
-Alternating antagonism
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Neurolinguistics of bilingualism
Hypotheses
-all languages represented in same areas
-all languages localized in separate areas
-specific bilingualism-related functional areas
-languages represented in same areas, butseparate neural circuits and seperate nerve cells– Related to implicit/explicit memory for different languages
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Neurolinguistics of bilingualism
Complex
-Impossible to predict recovery patterns taking into account the traditional variables
-Limitations of language test
-Brain imaging to the rescue?
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Neurolinguistics of bilingualism
Non-clinical neurolinguistics
-Large body of neuroimaging studies
-Neural networks underlying different domains language processing
-Has led to new discoveries
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Neurolinguistics of bilingualism
Clinical approach to multilingualism
-claim of different L2 localization–Scoresby-Jackson (1861)
–Dominant for over a century
–Now challenged by neuroimaging studies
– Distinction between language representation andlanguage control
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Neurolinguistics of bilingualism
Acquisition and processing of L2 grammar
-Declarative/procedural model–Lexical information: declarative
–Grammatical processing: procedural
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Neurolinguistics of bilingualism
Different localization
-Procedural system–Fronto-striatal network (Broca’s area and the basal ganglia)
-Declarative system–Left temporal areas
–Cf. regular vs. Irregular verbs
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Neurolinguistics of bilingualism
Regular verbs in English
-regular verbs–Most affected by Parkinson’s disease
-irregular verbs–Most affected by Huntington’s disease
(Both are striatal dysfunctions)
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Neurolinguistics of bilingualism
But …
-damage to basal ganglia has impact on cortical regions
-no association found by (Longworth et al., 2005) for English & by (Penke et al., 2005) for German
-neocortical classical language regions more important
-inhibition of competing alternatives
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Neurolinguistics of bilingualism
Basal ganglia
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Neurolinguistics of bilingualism
Basal ganglia
-higher-order motor control
-control of voluntary movement
-highly involved in learning and memory–Feedback processing
-language control
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Neurolinguistics of bilingualism
Implications for L2 processing
Will Broca’s area, along with the basal ganglia, be responsible only for L1 processing or will it also underlie processing of L2 grammar?
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Neurolinguistics of bilingualism
Neuroimaging to the rescue
To what extent is there functional neuroimaging evidence of the involvement of these brain structures in the acquisition of a second language?
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Neurolinguistics of bilingualism
Two models
-L2 grammar acquisition in adulthood does not rely on same brain structures as L1 (fronto-striatal network) (Ullman, 2001)
-neural differences between L1 & L2 speakers may disappear as proficiency increases (Green, 2003)
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Neurolinguistics of bilingualism
Grammatical processing
Wartenburger et al., 2003
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Neurolinguistics of bilingualism
Lexico-semantic processing
-L2-related differences found in low proficient and/or less exposed bilinguals (Perani et al., 2003; Pallier et al., 2003)
-greater engagement of LIFG & selective engagement PFC– Single word production paradigms– Lexical decision & semantic judgment– Story comprehension
– Involvement of temporal lobes in L2 vs activity in PFC
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Neurolinguistics of bilingualism
Why neural differences?
-Fact I: Broca’s area and temporal lobes less involved in L2 processing (for low-proficient and/or late learners)
-Fact II: PFC involvement higher in L2 processing (for …)
-Distinction between linguistic representation & language control
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Neurolinguistics of bilingualism
Prefrontal effect
-competition between lemmas in L1 & L2
– Inhibiting any active, non-target language
-interference from a prepotent concept name
-less effort lexical retrieval– From controlled to automatic processing
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Neurolinguistics of bilingualism
Explaining recovery patterns
Why should an L2 that is mastered with a low degree of proficiency be represented more extensively at the brain level?
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Neurolinguistics of bilingualism
Explaining recovery patterns
-Again, paramount is the distinction between
language specific neural representations & processing-specific demands
-Analogy with monolingual case–Cognitive effort reduced in a well-mastered task
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Neurolinguistics of bilingualism
Crucial role of prefrontal cortex
-strategic position & interconnectivity with a multitude
neocortical and subcortical areas (Abutalebi & Green, 2007)
-top/down control inhibitory mechanism vs.
more local and bottom-up inhibitory mechanism
-dedicated network of brain areas for language control
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Neurolinguistics of bilingualism
Mechanism of language control
-inhibition of a current task (speaking in language A) in favour of a new task (speaking in language B)– Application: language switching, translation, …
-withholding a potential prepotent response– Application: language selection, …
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Neurolinguistics of bilingualism
Language control network
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Neurolinguistics of bilingualism
Language control networks
-No single level of control–For example competition between lemmas, …
-Multiple neural levels of control involved–Also devoted to motor or cognitive control, …
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Neurolinguistics of bilingualism
Link between language and cognition
-what is the effect of using these cognitive control networks on non-verbal control tasks?– Less interference in a Simon task
– Highly controversial topic
– Does bilingualism improve selective attention?
– Or similar to switching between registers?