Cortical Thickness and Gyrification in Children with Developmental Dyslexia

Prior research has demonstrated a pattern of atypical neural structure and function within regions of the left hemisphere reading network in individuals with dyslexia compared to controls. However, studies of pediatric dyslexia are sparse, demonstrate variability in dyslexia classification, and yield inconsistent associations between cortical metrics and reading ability. This study investigated cortical metrics in typically developing readers (n=39) and children with dyslexia (n=37) as determined by deficient single word reading ability. Whole-brain vertex-wise analyses, performed using FreeSurfer, evaluated cortical thickness and local gyrification between reading groups, controlling for age. Following multiple comparison correction, readers with dyslexia demonstrated reduced cortical thickness within previously identified critical reading areas including: bilateral inferior-temporal, inferior-frontal, and occipito-parietal regions, along with left anterior cingulate cortex. In readers with dyslexia, thinner cortex was accompanied by increased gyrification in the cuneus and left inferior temporal cortex. The convergence of thinner and more gyrified cortex within the left inferior temporal region in children with dyslexia may reflect its early temporal role in processing word forms, and highlights the importance of the ventral stream for successful decoding. Reading fluency scores demonstrated a positive association with cortical thickness in right inferior frontal and bilateral inferior temporal cortices, while reading comprehension was significantly correlated with thickness across all regions.