Tracking the Roots of Reading Ability: White Matter Volume and Integrity Correlate with Phonological Awareness in Prereading and Early-Reading Kindergarten Children

Abstract

Developmental dyslexia, an unexplained difficulty in learning to read, has been associated with alterations in white matter organization as measured by diffusion-weighted imaging. It is unknown, however, whether these differences in structural connectivity are related to the cause of dyslexia or if they are consequences of reading difficulty (e.g., less reading experience or compensatory brain organization). Here, in 40 kindergartners who had received little or no reading instruction, we examined the relation between behavioral predictors of dyslexia and white matter organization in left arcuate fasciculus, inferior longitudinal fasciculus, and the parietal portion of the superior longitudinal fasciculus using probabilistic tractography. Higher composite phonological awareness scores were significantly and positively correlated with the volume of the arcuate fasciculus, but not with other tracts. Two other behavioral predictors of dyslexia, rapid naming and letter knowledge, did not correlate with volumes or diffusion values in these tracts. The volume and fractional anisotropy of the left arcuate showed a particularly strong positive correlation with a phoneme blending test. Whole-brain regressions of behavioral scores with diffusion measures confirmed the unique relation between phonological awareness and the left arcuate. These findings indicate that the left arcuate fasciculus, which connects anterior and posterior language regions of the human brain and which has been previously associated with reading ability in older individuals, is already smaller and has less integrity in kindergartners who are at risk for dyslexia because of poor phonological awareness. These findings suggest a structural basis of behavioral risk for dyslexia that predates reading instruction.

Enhancement of brain event-related potentials to speech sounds is associated with compensated reading skills in dyslexic children with familial risk for dyslexia

“…Structural connectivity and volume of the white matter tracks, left superior corona radiata and left arcuate fasciculus connecting anterior and posterior language regions of the human brain are deficient in adult dyslexics between regions of the reading network and related to poor reading skills ( Vandermosten, Boets, Poelmans, Sunaert, Wouters, & Ghesquière, 2012;Vandermosten, Boets, Wouters, & Ghesquière, 2012). In kindergartners at risk for dyslexia, better phonological awareness, but not rapid naming or letter naming, was positively correlated with the volume of the left arcuate fasciculus being smaller and having less integrity (Saygin et al, 2013). A consistent finding across neurofunctional studies is left ventral occipito-temporal dysfunction, which has been reported in both children and adults with dyslexia; hypoactiva-13 tion in superior temporal regions was found for adults only .…”

Distinguishing cause from effect – many deficits associated with developmental dyslexia may be a consequence of reduced and suboptimal reading experience

“…enough prereaders with and without familial and/or genetic risk of dyslexia, cf. Hakvoort, van der Leij, Maurits, Maassen, & van Zuijen, 2015;Saygin et al, 2013;Vandermosten et al, 2016;Willems, Jansma, Blomert, & Vaessen, 2016), and that reading experience is monitored meticulously throughout any study. Conducting such a study is no mean feat and will require a large, multiple lab effort.…”

The practical and principled problems with educational neuroscience.

“…For instance, Saygin et al (2013) found increased white matter was associated with increased phonological awareness skills of pre-reading and early-reading kindergarten children. Similarly, Meyers et al (2015) found evidence that increased white matter in kindergarten children predicted reading performance in Grade 3.…”