Language switching decomposed through MEG and evidence from bimodal bilinguals

A defining feature of human cognition is the ability to quickly and accurately alternate between complex behaviors. One striking example of such an ability is bilinguals’ capacity to rapidly switch between languages. This switching process minimally comprises disengagement from the previous language...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2018-09, Vol.115 (39), p.9708-9713
Main Authors: Blanco-Elorrieta, Esti, Emmorey, Karen, Pylkkänen, Liina
Format: Article
Language:English
Subjects:
Brain - physiology
Cognition
Cognition & reasoning
Cognition - physiology
Cortex (cingulate)
Decoding
Electroencephalography
Executive Function - physiology
Human performance
Humans
Language
Languages
Magnetic fields
Magnetoencephalography
Multilingualism
Prefrontal cortex
Sign Language
Social Sciences
Switching
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Summary:A defining feature of human cognition is the ability to quickly and accurately alternate between complex behaviors. One striking example of such an ability is bilinguals’ capacity to rapidly switch between languages. This switching process minimally comprises disengagement from the previous language and engagement in a new language. Previous studies have associated language switching with increased prefrontal activity. However, it is unknown how the subcomputations of language switching individually contribute to these activities, because few natural situations enable full separation of disengagement and engagement processes during switching. We recorded magnetoencephalography (MEG) from American Sign Language–English bilinguals who often sign and speak simultaneously, which allows to dissociate engagement and disengagement. MEG data showed that turning a language “off” (switching from simultaneous to single language production) led to increased activity in the anterior cingulate cortex (ACC) and dorsolateral prefrontal cortex (dlPFC), while turning a language “on” (switching from one language to two simultaneously) did not. The distinct representational nature of these on and off processes was also supported by multivariate decoding analyses. Additionally, Granger causality analyses revealed that (i) compared with “turning on” a language, “turning off” required stronger connectivity between left and right dlPFC, and (ii) dlPFC activity predicted ACC activity, consistent with models in which the dlPFC is a top–down modulator of the ACC. These results suggest that the burden of language switching lies in disengagement from the previous language as opposed to engaging a new language and that, in the absence of motor constraints, producing two languages simultaneously is not necessarily more cognitively costly than producing one.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.1809779115