White matter plasticity and reading instruction: Widespread anatomical changes track the learning process

Abstract

White matter tissue properties correlate with children's performance across domains ranging from reading, to math, to executive function. We use a longitudinal intervention design to examine experience-dependent growth in reading skills and white matter in a group of grade school aged, struggling readers. Diffusion MRI data were collected at regular intervals during an 8-week, intensive reading intervention. These measurements reveal large-scale changes throughout a collection of white matter tracts, in concert with growth in reading skill. Additionally, we identify tracts whose properties predict reading skill but remain fixed throughout the intervention, suggesting that some anatomical properties may stably predict the ease with which a child learns to read, while others dynamically reflect the effects of experience. These results underscore the importance of considering recent experience when interpreting cross-sectional anatomy-behavior correlations. Widespread changes throughout the white matter may be a hallmark of rapid plasticity associated with an intensive learning experience.peer-reviewed) is the author/funder. All rights reserved. No reuse allowed without permission.The copyright holder for this preprint (which was not . http://dx.doi.org/10.1101/268979 doi: bioRxiv preprint first posted online Feb. 22, 2018; 2 Skilled reading requires orchestration of a large cortical network, and individual differences in reading performance have been linked to the properties of white matter tracts connecting portions of this network specialized for processing visual, acoustic, and semantic features [1][2][3][4][5][6][7][8][9] .Although individual differences in white matter are thought to reflect the joint influence of genetics and experience [10][11][12] , white matter properties are often held to underlie variation in performance and to causally influence individual learning trajectories [13][14][15][16] . A number of recent studies, working within this framework, have identified features of the white matter that predict reading outcomes in dyslexia 17 , and reading-related skills, like phonological awareness, in prereading children 14,18,19 . The implication of these observations is that underlying anatomical differences may predestine certain individuals to struggle with learning to read. In this view, differences in white matter properties could be considered a reflection of intrinsic deficits, which might be relatively resistant to remediation, but which could plausibly be used for early identification of individuals in need of extra educational support 20 .Successfully relating anatomical differences with behavioral outcomes requires an understanding of the timescale over which white matter tissue properties exhibit experiencedependent change, and the anatomical specificity of these effects. White matter plasticity, including activity-dependent myelination and oligodendrocyte proliferation, has been observed in animal models over the time-scale of days to weeks [21][22][23][24] , and these effect...