Functional connectivity and structural changes in children's bilingual brains

 


This is the inferior frontal gyrus (IFG) and there are multiple researches to show that this part of the brain has a role in language processing. As a result, it has been proven that the IFG's functional connectivity and structure is different in bilingual adults than monolingual adults. However some of these changes occur in childhood whereas others occur later in childhood or adolescence. The "Young children in different linguistic environments : A multimodal neuroimaging study of the inferior frontal gyrus" research paper by Camilia Thieba exactly tried to find out how this area of the brain in childhood is affected by comparing bi/multilingual children to monolingual children. To do so, MRI and T1-weighted MRI  were used in this research to measure the functional connectivity and structure of the IFG. 

44 children were assessed in this research, 22 from a multilingual background and 22 from a monolingual background. The control variables in this research were :

- age

- sex

- right handed

- brain and psychological health

- first exposure of the child to the language(s)

- English ability ( phonological processing and speeded naming)

- Maternal education

- Household income

- % of time exposed to other language(s) other than English

- specific list of the languages, other than English, that the children could be exposed to

However there were a couple of limitations in this research, which include 

- The proficiency measures in the additional languages(s) were not measured which are proven to affect brain structure and functional connectivity.

- relatively small sample size 

- the number of languages to which the child is exposed to, apart from English, was not considered 

The main finding in this research is that the children growing up in a multilingual environment have a more integrated functional language network that is less functionally connected to parts of the default mode and ventral attention networks than children growing up in a monolingual environment. The results to prove this were :

- No significant difference in the IFG cortical structure between multilingual and monolingual children suggesting structural changes in the multilingual brain occur later in childhood or adolescence.

- Stronger connectivity from the IFG to other brain language regions in the children with more exposure to multiple languages suggesting functional brain changes happen during the process of learning a second language

- Multilingual children had increased functional connectivity between the IFG and the superior parietal cortex ( part of the dorsal attention network ) which could suggest two scenarios : these could justify the increased attention abilities demonstrated by bilingual compared to monolinguals as the dorsal attention network is related to orienting attention or it could represent the control mechanisms that are necessary to manage linguistic interactions in multilingual children. 

- The multilingual group had weaker connectivity from the IFG to areas of the ventral attention network (middle frontal gyrus) which is responsible for the response to relevant external stimuli. This may suggest that there is an increased cognitive demands for interference suppression

- The multilingual group also had weaker connectivity from the IFG to the default mode network (anterior cingulate gyrus and inferior parietal gyrus) which is active when an individual is not focused on any particular task

- The weaker connectivity detected between the IFG and the left inferior and middle temporal gyrus in children raised in a multilingual environment could reflect deficits in lexical access experienced by bilinguals as in adults, this weaker connectivity was associated with difficulties naming.

In conclusion, learning languages cause some changes in the brain's connectivity from a young age so in the process of learning a language. However other changes, such as structure of the brain, may occur later in life.



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