Abstract
Learning to read changes the brain language system. Phonological processing is the language domain most crucial for reading, but it is still unknown how reading acquisition modifies the neural phonological network in children who either develop dyslexia or are at risk of dyslexia. For the two first years of formal education, we followed 90 beginning readers with (n = 55) and without (n = 35) familial risk of dyslexia who became typical readers (n = 70) or developed dyslexia (n = 20). We used functional magnetic resonance imaging to identify the neural correlates of phonological awareness using an auditory rhyme judgment task. This task was applied when participants were starting formal education, and repeated 2 years later. By applying two alternative group splits, we analyzed the effects of dyslexia and the effects of familial risk of dyslexia separately. We found that the phonological brain network undergoes reorganization during the first 2 years of formal education. This process proceeds differently depending on the presence of a familial history of dyslexia and reading impairment. Typical readers without risk for dyslexia activate structures responsible for phonological processing already at the beginning of literacy. This group shows reduced brain activation over time during phonological processing, perhaps due to automatization of phonological skills. Children who develop reading impairment present a delay in the development of phonological structures such as the bilateral superior temporal gyri, left middle temporal gyrus, right insula and right frontal cortex, where we observed time and group interaction. Finally, typical readers with familial risk of dyslexia also present an atypical development of the neural phonological structures, visible both at the beginning of reading instruction and 2 years later. These children used a presumably efficient neural mechanism of phonological processing, based on the activation of the precentral and postcentral gyri, and achieved a typical level of phonological awareness.
Highlights
Learning to read is a long-lasting process which requires mastering a number of skills
Behavioral Results No significant differences in early reading and reading related tests were observed between children with and without a familial history of dyslexia, the groups differed in parental scores in the Adult Reading History Questionnaire and in home literacy environment
In-Scanner Performance No significant differences in accuracy in in-scanner tasks were observed between children with and without a familial history of dyslexia
Summary
Learning to read is a long-lasting process which requires mastering a number of skills. The brain network responsible for phonological processing includes mostly left hemisphere areas like the inferior parietal lobule (including supramarginal and angular gyri), inferior frontal cortex, postcentral and precentral gyri, superior and middle temporal gyri, and fusiform and dorsolateral prefrontal cortex (Poldrack et al, 1999; Booth et al, 2006; Hoeft et al, 2006; Bitan et al, 2007; Cao et al, 2008; Kovelman et al, 2012). Patterns of brain activation during phonological processing differ between dyslexic and typical readers and have been observed with functional magnetic resonance imaging (fMRI; Richlan et al, 2011). Only a few fMRI experiments have explored phonological processing independent of reading abilities using a task based on spoken language (Desroches et al, 2010; Kovelman et al, 2012; Raschle et al, 2012, 2014; Debska et al, 2016; Yu et al, 2018). Studies on dyslexic and typically reading children have produced inconsistent results: Desroches et al (2010) reported hypoactivation of the left fusiform gyrus in the dyslexic group while Kovelman et al (2012) found hypoactivation only in the left dorsolateral prefrontal cortex
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