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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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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

-What is the study object?

–Neurolinguistics studies the cognitive processes underlying language processing

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Principles

-Traditional language testing tells us very little about the cognitive processes that underlie language processing.

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Principles

-Language processing in the brain shares many cognitive processes with other cognitive domains.

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Principles

-Implicit acquisition of language leads to recruitment of similar cognitive mechanisms as explicit acquisition with higher learning gains.

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Principles

-If proficiency is similar, younger learners always show more efficient language processing in the brain.

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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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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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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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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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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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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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Dissociated recovery

-Parallel recovery

-Differential recovery

-Selective recovery

-Mixed recovery

-Successive recovery

-Alternating antagonism

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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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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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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

-Declarative/procedural model–Lexical information: declarative

–Grammatical processing: procedural

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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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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

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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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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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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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Grammatical processing

Wartenburger et al., 2003

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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 network

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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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