Existing studies have revealed that language acquisition influences both structure and function of the brain. However, whether the acquisition of second language at different periods of life alters functional network organization in different ways remains unclear. Here, functional magnetic resonance imaging data of 30 English-speaking monolingual controls, 52 Spanish-English bilinguals, including 22 early bilinguals who began learning a second language before the age of ten, and 30 late bilinguals who started learning their second language at age fourteen or later were collected from OpenNeuro database. Topological metrics of resting-state functional networks were computed via graph theoretical approach, including small-world attributes, betweenness centrality, network efficiency, and rich and diverse-clubs that characterize functional integration and segregation of the networks. Results showed remarkable increases of network efficiency and rich-club functional connectivity in the early bilinguals relative to the monolingual controls, whereas the network organization of the late bilinguals did not significantly differ from the monolingual controls. The increased functional connectivity positively correlated with the number of languages exposed. Furthermore, the rostroventral area of the left cingulate gyrus that played an important role in both rich and diverse-clubs showed higher betweenness centrality in the EB than in the other two groups. These findings demonstrated early acquisition of second language modulated functional brain networks toward a more efficient and strengthened organization.
Background and purposeGrowing evidence suggests that abnormalities in brain–gut–microbiome (BGM) interactions are involved in the pathogenesis of irritable bowel syndrome (IBS). Our study aimed to explore alterations in dynamic functional connectivity (DFC), the gut microbiome and the bidirectional interaction in the BGM.MethodsResting‐state functional magnetic resonance imaging (rs‐fMRI), fecal samples and clinical chacteristics were collected from 33 IBS patients and 32 healthy controls. We performed a systematic DFC analysis on rs‐fMRI. The gut microbiome was analyzed by 16S rRNA gene sequencing. Associations between DFC characteristics and microbial alterations were explored.ResultsIn the DFC analysis, four dynamic functional states were identified. IBS patients exhibited increased mean dwell and fraction time in State 4, and reduced transitions from State 3 to State 1. Aberrant temporal properties in State 4 were only evident when choosing a short window (36 s or 44 s). Decreased functional connectivity (FC) variability was found in State 1 and State 3 in IBS patients, two of which (independent component [IC]51‐IC91, IC46‐IC11) showed significant correlations with clinical characteristics. Additionally, we identified nine significantly differential abundances in microbial composition. We also found that IBS‐related microbiota were associated with aberrant FC variability, although these exploratory results were obtained at an uncorrected threshold of significance.ConclusionsAlthough future studies are needed to confirm our results, the findings not only provide a new insight into the dysconnectivity hypothesis in IBS from a dynamic perspective, but also establish a possible link between DFC and the gut microbiome, which lays the foundation for future research on disrupted BGM interactions.
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