title: Effects of Early and Late Bilingualism on Resting-State Functional Connectivity.
abstract: Of current interest is how variations in early language experience shape patterns of functional connectivity in the human brain. In the present study, we compared simultaneous (two languages from birth) and sequential (second language learned after age 5 years) bilinguals using a seed-based resting-state MRI approach. We focused on the inferior frontal gyrus (IFG) as our ROI, as recent studies have demonstrated both neurofunctional and neurostructural changes related to age of second language acquisition in bilinguals in this cortical area. Stronger functional connectivity was observed for simultaneous bilinguals between the left and right IFG, as well as between the inferior frontal gyrus and brain areas involved in language control, including the dorsolateral prefrontal cortex, inferior parietal lobule, and cerebellum. Functional connectivity between the left IFG and the right IFG and right inferior parietal lobule was also significantly correlated with age of acquisition for sequential bilinguals; the earlier the second language was acquired, the stronger was the functional connectivity. In addition, greater functional connectivity between homologous regions of the inferior frontal gyrus was associated with reduced neural activation in the left IFG during speech production. The increased connectivity at rest and reduced neural activation during task performance suggests enhanced neural efficiency in this important brain area involved in both speech production and domain-general cognitive processing. Together, our findings highlight how the brain's intrinsic functional patterns are influenced by the developmental timeline in which second language acquisition occurs.
  
  
  CONCLUSIONS
  Of current interest is how early life experience leaves its footprint on brain structure and function. In this regard, bilingualism provides an optimal way to determine the effects of the timing of language learning because a second language can be learned from birth or later in life. We used resting-state fMRI to look at simultaneous and sequential bilinguals who differed only in age of acquisition, and found stronger connectivity between language and cognitive control regions in bilinguals who learned their two languages simultaneously, a pattern that was associated with more efficient brain activation during speech. Our findings highlight how functional connections in the brain differ depending upon when learning takes place.
authors.affiliation: Cognitive Neuroscience Unit, Montreal Neurological Institute, Montreal, Quebec H3A 2B4, Canada, Centre for Research on Brain, Language, and Music, McGill University, Montreal, Quebec H3G 2A8, Canada, and jonathan.berken@gmail.com.
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Berken
authors.affiliation: Cognitive Neuroscience Unit, Montreal Neurological Institute, Montreal, Quebec H3A 2B4, Canada.
authors.forename: Xiaoqian
authors.initials: X
authors.lastname: Chai
authors.affiliation: Cognitive Neuroscience Unit, Montreal Neurological Institute, Montreal, Quebec H3A 2B4, Canada.
authors.forename: Jen-Kai
authors.initials: JK
authors.lastname: Chen
authors.affiliation: Centre for Research on Brain, Language, and Music, McGill University, Montreal, Quebec H3G 2A8, Canada, and Haskins Laboratories, New Haven, Connecticut 06511.
authors.forename: Vincent L
authors.initials: VL
authors.lastname: Gracco
authors.affiliation: Cognitive Neuroscience Unit, Montreal Neurological Institute, Montreal, Quebec H3A 2B4, Canada, Centre for Research on Brain, Language, and Music, McGill University, Montreal, Quebec H3G 2A8, Canada, and.
authors.forename: Denise
authors.initials: D
authors.lastname: Klein
mesh_terms: D000328:Adult; D001921:Brain / Q000098:blood supply / Q000502:physiology*; D001931:Brain Mapping; D005260:Female; D007839:Functional Laterality; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D019303:Multilingualism; D009434:Neural Pathways / Q000098:blood supply / Q000502:physiology; D010100:Oxygen / Q000097:blood; D012044:Regression Analysis; D012146:Rest / Q000502:physiology*; D013060:Speech / Q000502:physiology*; D013997:Time Factors; D055815:Young Adult
chemical_list: D010100:Oxygen
keywords: bilingualism; brain development; early experience; inferior frontal gyrus; language; resting-state functional connectivity
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