The optic radiations and reading development: a longitudinal study of children born term and preterm

Purpose To determine if development of single-word reading between ages 6 and 8 years was related to change in a microstructural property of the optic radiations (OR), white matter circuits that are not typically associated with language or reading and if the patterns of association were similar in children born full term (FT) and preterm (PT). Methods FT (n=34) and PT (n=34) were assessed using the Woodcock Reading Mastery Test at 6, 7, and 8. Word Identification raw score was the outcome measure. Diffusion MRI was acquired at 6 and 8 years using a 96-direction scan (b=2500 sec/mm 2 ). Probabilistic tractography identified left and right OR. We used linear mixed models to determine if change in fractional anisotropy (FA) averaged across the left and right OR was associated with growth in reading. Results The rate of reading growth was similar in both groups. FA of the OR was higher in children born FT than PT at age 8. Change in FA of the OR from age 6 to 8 was negatively associated growth in reading across both birth groups. Conclusion Individual differences in the rate of development in reading skills was associated with individual differences in the change in FA of the visual pathways in both children born FT and PT. Decreasing FA implicates increasing axonal diameter and/or complexity in fiber structure as the drivers of faster reading development. Highlights The rate of reading growth was similar in children born full term and preterm FA of the optic radiations increased from age 6 to 8 years in both groups FA of the optic radiations was higher in full term than preterm children at age 8 Decreasing FA in optic radiations was associated with accelerated reading growth Associations of FA in optic radiations and reading were similar in two birth groups