Inside the Bilingual Brain
Researchers link strength of brain connections to language learning success.
Posted Feb 10, 2016
Post written by Aneta Pavlenko.
Can scientists look at our brains and predict whether some of us will make more successful language learners than others? A recent study published by the Journal of Neuroscience suggests that they can. To get a peek inside the bilingual brain, Xiaoqian Chai and associates at McGill University use functional Magnetic Resonance Imaging (fMRI), a neuroimaging procedure that measures changes in blood oxygenation level as a way to understand brain activity (higher levels of oxygenated haemoglobins mean more activity). This procedure is helping them to study connections between different brain areas that talk to each other in the process of second language (L2) learning and use.
To see if individual differences in brain connectivity can predict L2 learning success, the researchers recruited 15 English-speaking students who arrived in Montreal from other Canadian provinces, as well as from Australia, the UK, and the USA, and who did not know much French. fMRI was used to measure connectivity in two brain areas: the left frontal region linked to verbal fluency and the left ventral temporal-occipital cortex, aka the visual word form area, where signs on the page are converted into phonemes and words. To test participants’ verbal and reading fluency, the researchers asked them to speak for 2 minutes and to read passages out loud in both languages.
Then the students took an intensive French immersion course that focused on reading and conversational competence required for higher-level communication and that lasted 12 weeks (6 hrs a day, 5 days a week). After the course ended, the researchers once again tested verbal fluency, asking participants again to speak for 2 minutes in French and English. The total number of unique words employed correctly was used as a measure of verbal fluency (they called this lexical retrieval). They also asked the students to read passages again and used the number of words per minute as a measure of reading fluency. The analysis of pre- and post-immersion L1 English performance revealed no differences in lexical retrieval or reading speed. In L2 French, on the other hand, the students made significant improvement, both in the number of unique words produced and in reading speed.
The researchers then correlated the L2 performance measures with resting-state brain connectivity measured before the French course and found two interesting patterns. Individuals with stronger connectivity between the left frontal region and the left posterior superior temporal gyrus (STG) showed greater improvement in the number of unique words produced (lexical retrieval) in L2 French, while individuals with stronger connectivity between the visual word form area and left middle STG showed greater improvement in reading speed in L2 French.
These findings were immediately reported by the media as a claim that some brains are better wired for language learning than others. In fact, things are not as simple, as the authors showed in another study that came out in the same journal a week later. In this study, they used fMRI once again to compare resting-state brain connectivity in a different area of the brain – the inferior frontal gyrus – and in a different group of participants. This time, the participants were 16 French-English simultaneous bilinguals, and 18 sequential bilinguals, the latter having learned their L2, either French or English, after the age of 5. The results revealed that in simultaneous bilinguals the connectivity between the brain hemispheres is greater than in sequential bilinguals, who appear to rely more on the left hemisphere.
These findings raise an intriguing possibility that connectivity may be malleable, at least in some brain areas, and the very experience of learning another language can change our internal wiring making us better learners. To confirm this hypothesis, neuroscientists will need to conduct longitudinal studies, following a group of learners as they go about learning a language until they become bilingual, so let’s stay tuned.
For a full list of "Life as a bilingual" blog posts by content area, see here.
Photo of a magnetic resonance image (MRI) of the brain from Shutterstock.
Berken, J., Chai, X., Chen, J.-K., Gracco, V., & D. Klein (2016) Effects of early and late bilingualism on resting-state functional connectivity. The Journal of Neuroscience, January 27, 2016, 36, 4, 1165-1172.
Chai, X., Berken, J., Barbeau, E., Soles, J., Callahan, M., Chen, J.-K., & D. Klein (2016) Intrinsic functional connectivity in the adult brain and success in second-language learning. The Journal of Neuroscience, January 20, 2016, 36, 3, 755-761.
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