Abstract
During reading acquisition, neural reorganization of the human brain facilitates the integration of letters and speech sounds, which enables successful reading. Neuroimaging and behavioural studies have established that impaired audiovisual integration of letters and speech sounds is a core deficit in individuals with developmental dyslexia. This longitudinal study aimed to identify neural and behavioural markers of audiovisual integration that are related to future reading fluency. We simulated the first step of reading acquisition by performing artificial-letter training with prereading children at risk for dyslexia. Multiple logistic regressions revealed that our training provides new precursors of reading fluency at the beginning of reading acquisition. In addition, an event-related potential around 400 ms and functional magnetic resonance imaging activation patterns in the left planum temporale to audiovisual correspondences improved cross-validated prediction of future poor readers. Finally, an exploratory analysis combining simultaneously acquired electroencephalography and hemodynamic data suggested that modulation of temporoparietal brain regions depended on future reading skills. The multimodal approach demonstrates neural adaptations to audiovisual integration in the developing brain that are related to reading outcome. Despite potential limitations arising from the restricted sample size, our results may have promising implications both for identifying poor-reading children and for monitoring early interventions.
Highlights
During reading acquisition, neural reorganization of the human brain facilitates the integration of letters and speech sounds, which enables successful reading
35 prereading children at varying risk for developmental dyslexia were tested for precursor skills of reading, participated in computerized, artificial-letter training, and performed an implicit audiovisual target detection task in a simultaneous EEG-functional magnetic resonance imaging (fMRI) session during which the trained grapheme–phoneme correspondences were presented (Supplementary Table S1)
This result is in line with previous evidence that rapid automatized naming (RAN) is a robust precursor of reading fluency in European languages[31] and of reading outcome in various alphabetic and non-alphabetic languages[32]
Summary
Neural reorganization of the human brain facilitates the integration of letters and speech sounds, which enables successful reading. Neuroimaging and behavioural studies have established that impaired audiovisual integration of letters and speech sounds is a core deficit in individuals with developmental dyslexia. This longitudinal study aimed to identify neural and behavioural markers of audiovisual integration that are related to future reading fluency. Deviant neurobiological development of the visual and phonological neural circuits during reading acquisition probably leads to impaired automatization in learning letter–speech sound associations, a core deficit of dyslexic children[14]. Previous studies have shown that the brain activation difference between congruent and incongruent audiovisual letter–speech sound associations is larger in normal-reading children and adults than in children and adults with developmental dyslexia[16,17,18,19]. Filling this research gap is highly relevant to determining the neurobiological mechanisms that underlie the audiovisual integration deficit at the very early learning stage that precedes reading acquisition
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