Investigating the impact of early literacy training on white matter structure in prereaders at risk for dyslexia.

Recent prereading evidence demonstrates that white matter alterations are associated with dyslexia even before the onset of reading instruction. At the same time, remediation of reading difficulties is suggested to be most effective when provided as early as kindergarten, yet evidence is currently lacking on the early neuroanatomical changes associated with such preventive interventions. To address this open question, we investigated white matter changes following early literacy intervention in Dutch-speaking prereaders (aged 5-6 years) with an increased cognitive risk for developing dyslexia. Diffusion-weighted images were acquired before and after a 12-week digital intervention in three groups: (i) at-risk children receiving phonics-based training (n = 31); (ii) at-risk children engaging with active control training (n = 25); and (iii) typically developing children (n = 27) receiving no intervention. Following automated quantification of white matter tracts relevant for reading, we first examined baseline differences between at-risk and typically developing children, revealing bilateral dorsal and ventral differences. Longitudinal analyses showed that white matter properties changed within the course of the training; however, the absence of intervention-specific results suggests that these changes rather reflect developmental effects. This study contributes important first insights on the neurocognitive mechanisms of intervention that precedes formal reading onset.