neurolinguistics of bilingualismii - vrije universiteit...
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23-11-2011 1Herhaling titel van presentatie
Neurolinguistics of Bilingualism: Neuroimaging Multilinguals
Esli Struys
Linguistics & Neurosciences, Class 6
23-11-2011 2
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Non-clinical neurolinguistics
-Large body of neuroimaging studies
-Neural networks underlying different domains language processing
-Has led to new discoveries
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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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Acquisition and processing of L2 grammar
-L1 grammar generally acquiredimplicitly, L2 grammar acquiredexplicitly (Paradis, 2004)
-Declarative/procedural model–Monolinguals: words >< grammatical rules
–Bilinguals: words >< grammatical rules
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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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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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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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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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Basal ganglia
-higher-order motor control
-control of voluntary movement
-highly involved in learning and memory–Feedback processing
-language control
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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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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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Artificial grammar learning
-increasing proficiency leads toincreased recruitment of Broca’s area
-L2 acquisition through existing L1 syntax network (Opitz & Friederici, 2004)
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Wartenburger et al., 2003
-research design that enablescomparison between high and low proficient late bilinguals
-AoA more important than Proficiency for localization L2 grammar processing
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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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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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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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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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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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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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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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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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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?
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