Abstract
Word learning plays a central role in language development and is a key predictor for later academic success. The underlying neural basis of successful word learning in children is still unknown. Here, we took advantage of the opportunity afforded by diffusion-weighted magnetic resonance imaging to investigate neural plasticity in the white matter of typically developing preschool children as they learn words. We demonstrate that after 3 weeks of word learning, children showed significantly larger increases of fractional anisotropy (FA) in the left precentral white matter compared to two control groups. Average training accuracy was correlated with FA change in the white matter underlying the left dorsal postcentral gyrus, with children who learned more slowly showing larger FA increases in this region. Moreover, we found that the status of white matter in the left middle temporal gyrus, assumed to support semantic processes, is predictive for early stages of word learning. Our findings provide the first evidence for white matter plasticity following word learning in preschool children. The present results on learning novel words in children point to a key involvement of the left fronto-parietal fiber connection, known to be implicated in top-down attention as well as working memory. While working memory and attention have been discussed to participate in word learning in children, our training study provides evidence that the neural structure supporting these cognitive processes plays a direct role in word learning.
Highlights
Learning single words is the way children break into the human communication system, and the number of words a child knows is a key predictor for later academic success (Morgan et al 2015; Bleses et al 2016)
We show that after 3 weeks of learning novel words for novel objects, typically developing preschool-aged children demonstrate changes in white matter microstructure, that the change in fractional anisotropy (FA) is related to word learning success, and that white matter structure plays a predictive role in explaining individual differences in word learning ability in young children
We examined the alignment of FA maps from scan 1 and scan 2 within participants to rule out that any potential group differences in FA change were driven by misalignment
Summary
Learning single words is the way children break into the human communication system, and the number of words a child knows is a key predictor for later academic success (Morgan et al 2015; Bleses et al 2016). The goal of the present study is to investigate the white matter structures involved in word learning in preschool-aged children by measuring possible structural changes in the brain as a consequence of word learning. Recent results coming from studies using several different methods including magnetoencephalography (MEG), as well as functional and structural magnetic resonance imaging (MRI), have shed light on this process in adults (Hofstetter et al 2017; Bakker-Marshall et al 2018; Berens et al 2018). One study has shown that in adults, word learning leads to white matter changes in regions of the language network. After 1 h of word learning, structural changes in the white matter of the parietal lobe were found and changes in the superior longitudinal fascicle correlated with the lexical learning rate (Hofstetter et al 2017)
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