Abstract
.Significance: Early monolingual versus bilingual experience induces adaptations in the development of linguistic and cognitive processes, and it modulates functional activation patterns during the first months of life. Resting-state functional connectivity (RSFC) is a convenient approach to study the functional organization of the infant brain. RSFC can be measured in infants during natural sleep, and it allows to simultaneously investigate various functional systems. Adaptations have been observed in RSFC due to a lifelong bilingual experience. Investigating whether bilingualism-induced adaptations in RSFC begin to emerge early in development has important implications for our understanding of how the infant brain’s organization can be shaped by early environmental factors.Aims: We attempt to describe RSFC using functional near-infrared spectroscopy (fNIRS) and to examine whether it adapts to early monolingual versus bilingual environments. We also present an fNIRS data preprocessing and analysis pipeline that can be used to reliably characterize RSFC in development and to reduce false positives and flawed results interpretations.Methods: We measured spontaneous hemodynamic brain activity in a large cohort () of 4-month-old monolingual and bilingual infants using fNIRS. We implemented group-level approaches based on independent component analysis to examine RSFC, while providing proper control for physiological confounds and multiple comparisons.Results: At the group level, we describe the functional organization of the 4-month-old infant brain in large-scale cortical networks. Unbiased group-level comparisons revealed no differences in RSFC between monolingual and bilingual infants at this age.Conclusions: High-quality fNIRS data provide a means to reliably describe RSFC patterns in the infant brain. The proposed group-level RSFC analyses allow to assess differences in RSFC across experimental conditions. An effect of early bilingual experience in RSFC was not observed, suggesting that adaptations might only emerge during explicit linguistic tasks, or at a later point in development.
Highlights
Language acquisition begins about 3 months prior to birth when infants are able to hear spoken language.[1]
An effect of early bilingual experience in resting-state functional connectivity (RSFC) was not observed, suggesting that adaptations might only emerge during explicit linguistic tasks, or at a later point in development
All the participants had recordings with a duration of 9 min, which were input for data analysis with temporal group ICA (tGICA) and connectome-based ICA (connICA)
Summary
Language acquisition begins about 3 months prior to birth when infants are able to hear spoken language.[1]. The intrinsic functional organization of the infant brain described by RSFC can be modulated by various pre- and postnatal factors.[21,22,23] As measured by functional magnetic resonance imaging (fMRI), premature and full-term infants show different RSFC patterns.[24,25] It has been suggested that the configuration and maturational course of functional connectivity differs in typical and atypical functional brain development.[26,27] In addition, it has been proposed that early environmental factors can modify RSFC, including caregivers’ education level, or socioeconomic status.[28] Based on these observations, the present study aims to assess whether the brain’s functional connectivity begins to adapt to a bilingual environment as early as 4 months of age, by the time neural and behavioral responses to external stimuli already differ across monolingual and bilingual infants. Bilinguals might show a stronger functional connectivity in networks involving frontal regions
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