Children With Dyslexia and Familial Risk for Dyslexia Present Atypical Development of the Neuronal Phonological Network

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.

Brain dynamics of (a)typical reading development—a review of longitudinal studies

“…For phonological skills acquired earlier than reading, the development of associated phonological networks was delayed in poor reading children. The bilateral STG, left middle temporal gyrus, right insula, and frontal cortex were engaged by typical readers during auditory rhyming at the beginning of formal education and by dyslexic readers two years later 48 . Similarly, a developmental delay in the functional connectivity of the reading network was suggested by the other study 43 .…”

“…In an auditory phonological task, a developmental decrease in activation in the left inferior parietal cortex (IPC) and bilateral precuneus in typical readers from the beginning of formal education until the emergent reading stage (5 to 7–9 years of age) was reported. Another study 48 revealed reduced activity in the left perisylvian cortex (including IPC) for the auditory rhyming task in typical readers after the first 2 years of formal education, which was more pronounced in children without familial history of dyslexia. Functional connectivity analysis revealed that the connection strength between the left IPC, left IFG, left vOT, and right angular gyrus co‐developed with the growth of phonological skills 49 .…”

Treating developmental dyslexia using transcranial stimulation combined with a reading stimulation program: A pilot study

“…Magnetic resonance studies confirm abnormal and/or hypoactivation of temporo-occipital, temporo-parietal, left lower parietal, as well as the anterior and posterior cingulate regions (posterior areas of the left brain [2,3]. One study also found greater activation of the temporal region of right hemisphere in individuals with DD [3].…”

“…Developmental dyslexia (DD) are a neurobiological disorder characterized mainly by an impaired ability to decode and automatically, precisely recognize written words [1]. Magnetic resonance studies confirm abnormal and/or hypoactivation of temporo-occipital, temporo-parietal, left lower parietal, as well as the anterior and posterior cingulate regions (posterior areas of the left brain [2,3]. One study also found greater activation of the temporal region of right hemisphere in individuals with DD [3].…”

Categorical and Dimensional Diagnoses of Dyslexia: Are They Compatible?

“…The brains of children with dyslexia show peculiarities that can affect various regions, including for example the visual word form area ( Dehaene and Cohen, 2011 ), Broca’s area ( Paulesu et al, 2001 ), the magnocellular pathway ( Stein, 2001 ) and the cerebellum ( Nicolson et al, 2001 ). However, these patterns are not consistent across subjects ( Kraft et al, 2016 ; Łuniewska et al, 2019 ), and thus behavioral tasks remain the most effective assessment available ( Fletcher, 2009 ; Ramus et al, 2018 ).…”