ABSTRACT
The aim of this study was to determine the effect of a computerized executive functions (EFs)-based reading intervention on neural circuits supporting EFs and visual attention. Seed-to-voxel functional connectivity analysis was conducted focusing on large-scale attention system brain networks, during an fMRI reading fluency task. Participants were 8- to 12-year-old English-speaking children with dyslexia (n = 43) and typical readers (n = 36) trained on an EFs-based reading training (n = 40) versus math training (n = 39). Training duration was 8 weeks. After the EFs-based reading intervention, children with dyslexia improved their scores in reading rate and visual attention (compared to math intervention). Neurobiologically, children with dyslexia displayed an increase in functional connectivity strength after the intervention between the cingulo-opercular network and occipital and precentral regions. Noteworthy, the functional connectivity indices between these brain regions showed a positive correlation with speed of processing and visual attention scores in both pretest and posttest. The results suggest that reading improvement following an EFs-based reading intervention involves neuroplastic connectivity changes in brain areas related to EFs and primary visual processing in children with dyslexia. Our results highlight the need for training underlying cognitive abilities supporting reading, such as EFs and visual attention, in order to enhance reading abilities in dyslexia.
ABSTRACT
The asynchrony theory of dyslexia postulates weaker visual (orthographical processing) and auditory (phonological processing) network synchrony in dyslexic readers. The weaker visual-auditory network synchronization is suggested to contribute to slow processing speed, which supports cognitive control, contributing to single-word reading difficulty and lower reading fluency. The current study aims to determine the neurobiological signature for this theory and to examine if prompting enhanced reading speed through deleted text is associated with a greater synchronization of functional connectivity of the visual and auditory networks in children with dyslexia and typical readers (TRs). We further aimed to determine if the change in visual-auditory connectivity prompted by deleted text is associated with reading fluency and processing speed abilities. Nineteen children with dyslexia and 21 typical readers ages 8-12 years old participated in a fMRI under two types of reading conditions: a still text condition and deleted text condition, in which letters was sequentially deleted from the screen. Effects of diagnostic group and condition on functional connectivity (FC) of visual and auditory networks were examined. Results revealed a significant overall effect of condition with a marginally significant Group × Condition interaction, such that as compared with TRs, children with dyslexia showed a significantly greater increase in visual-auditory FC between the still and deleted text conditions. Additionally, for children with dyslexia, this FC increase was significantly correlated with better reading fluency and verbal/nonverbal processing speed. These results support a relationship between the synchronization of the visual and auditory networks, fluent reading and increased speed of processing abilities in children with dyslexia, which can help guide fluency-based intervention strategies.
ABSTRACT
Poor phonological processing has typically been considered the main cause of dyslexia. However, visuo-attentional processing abnormalities have been described as well. The goal of the present study was to determine the involvement of visual attention during fluent reading in children with dyslexia and typical readers. Here, 75 children (8-12 years old; 36 typical readers, 39 children with dyslexia) completed cognitive and reading assessments. Neuroimaging data were acquired while children performed a fluent reading task with (a) a condition where the text remained on the screen (Still) versus (b) a condition in which the letters were being deleted (Deleted). Cognitive assessment data analysis revealed that visual attention, executive functions, and phonological awareness significantly contributed to reading comprehension in both groups. A seed-to-voxel functional connectivity analysis was performed on the fluency functional magnetic resonance imaging task. Typical readers showed greater functional connectivity between the dorsal attention network and the left angular gyrus while performing the Still and Deleted reading tasks versus children with dyslexia. Higher connectivity values were associated with higher reading comprehension. The control group showed increased functional connectivity between the ventral attention network and the fronto-parietal network during the Deleted text condition (compared with the Still condition). Children with dyslexia did not display this pattern. The results suggest that the synchronized activity of executive, visual attention, and reading-related networks is a pattern of functional integration which children with dyslexia fail to achieve. The present evidence points toward a critical role of visual attention in dyslexia.
