Brain Structural Connectivity and Morphological Awareness Mediate the Association Between Home Literacy Environment and Reading Outcomes in Children With Family History of Reading Difficulties.

Previous studies have shown that higher socioeconomic status (SES) and richer home literacy environment (HLE) are associated with better reading outcomes in children with family risk for reading difficulties (RD). Yet, the cognitive and neural mechanisms underlying this association remain understudied. This study sought to fill in the gap using both behavioral and neuroimaging methodologies. Eighty-one native Mandarin-speaking children (age = 8.7-12.0 years) and their parents were recruited. Family history (FH) of RD and home environmental factors (SES and HLE) were collected, as well as children's diffusion MRI, reading-related cognitive skills (rapid automatized naming [RAN], phonological awareness [PA], and morphological awareness [MA]), and reading outcomes. Participants were divided into the following groups according to their FH of RD and current reading status: children with a FH of RD who showed typical development (FH+TD) or who developed RD (FH+RD), and a typically developing control group without a FH (FH-TD). Chain mediation analyses showed that in FH+TD, the number of children's books (NCB) was linked to the axial diffusivity (AxD) of children's right superior longitudinal fasciculus (rSLF). This neural metric was further linked to children's silent reading comprehension (SRC) via their MA. No such mediation relationship was shown in either FH+RD or FH-TD. These results suggest that reading-related cognitive skills constitute important pathways linking HLE and reading outcomes in at-risk children who developed typical reading skills, while the right-hemispheric white matter fiber tract may serve as one possible neural intermediary. Our findings have educational implications for developing early interventions that focus on enriching HLE to help mitigate the risk of RD. SUMMARY: Number of children's books (NCB) is uniquely associated with reading development in children with a family history (FH) of reading difficulties (RD) who nevertheless develop typical reading abilities. Rapid automatized naming (RAN) serves as a significant cognitive mediator for oral reading fluency (ORF), and morphological awareness (MA) for silent reading comprehension (SRC). One possible neural mechanism underlying the NCB → MA → SRC mediation pathway could be the white matter structure, rSLF-AxD. An updated operational definition is proposed and applied to identify protective factors in children at risk for RD. The chain mediation method is used to examine the multi-level pathways (environment-brain-cognition-behavior), as hypothesized by the Multiple Deficit Model (MDM) of reading development.