Abstract
Skilled reading requires orchestration of a large cortical network, and individual differences in reading performance have previously been linked to properties of relevant anatomical connections. However, it is not known how experience shapes this network, or whether correlations between anatomy and behavior are stable. To investigate the relationship between reading experience, reading skills, and white matter properties, we carried out a longitudinal study in children with reading difficulties (n=23, ages 6-12) who participated in an 8-week, intensive reading intervention. Along with behavioral measures, we collected diffusion MRI data over 4 sessions, separated by 2-week intervals. We first examined a set of white matter tracts considered to be part of the core circuitry for reading: the occipital callosal connections, left arcuate fasciculus (AF), and left inferior longitudinal fasciculus (ILF). Over the intervention, we observed changes in diffusion properties within the latter two tracts. Specifically, mean diffusivity (MD) decreased in the AF and ILF as a function of reading experience. In contrast, diffusion properties were stable in the occipital callosal connections. We next examined the relationship between MD values and reading skills. Only the callosal fibers clearly predicted reading skills in the intervention subjects. We therefore suggest that differences in MD within occipital callosal connections reflect relatively stable anatomical variation, which predicts reading skill but does not change during short-term, intensive training. Finally, to examine the anatomical specificity of intervention-driven changes, we performed hierarchical clustering based on the correlations between linear growth rates in 16 anatomical tracts. This analysis identified a cluster comprising the main cortical association tracts (left arcuate, left and right ILF, SLF, IFOF, and uncinate), which have previously been implicated in reading-related tasks. Large-scale change within this network may be a hallmark of rapid, short-term plasticity associated with intensive training of reading skills.
Meeting abstract presented at VSS 2017