Neural systems predicting long-term outcome in dyslexia

Abstract

Individuals with developmental dyslexia vary in their ability to improve reading skills, but the brain basis for improvement remains largely unknown. We performed a prospective, longitudinal study over 2.5 y in children with dyslexia (n = 25) or without dyslexia (n = 20) to discover whether initial behavioral or brain measures, including functional MRI (fMRI) and diffusion tensor imaging (DTI), can predict future long-term reading gains in dyslexia. No behavioral measure, including widely used and standardized reading and language tests, reliably predicted future reading gains in dyslexia. Greater right prefrontal activation during a reading task that demanded phonological awareness and right superior longitudinal fasciculus (including arcuate fasciculus) white-matter organization significantly predicted future reading gains in dyslexia. Multivariate pattern analysis (MVPA) of these two brain measures, using linear support vector machine (SVM) and cross-validation, predicted significantly above chance (72% accuracy) which particular child would or would not improve reading skills (behavioral measures were at chance). MVPA of whole-brain activation pattern during phonological processing predicted which children with dyslexia would improve reading skills 2.5 y later with >90% accuracy. These findings identify right prefrontal brain mechanisms that may be critical for reading improvement in dyslexia and that may differ from typical reading development. Brain measures that predict future behavioral outcomes (neuroprognosis) may be more accurate, in some cases, than available behavioral measures.inferior frontal gyrus | prediction | compensation | fractional anisotropy | rhyming D evelopmental dyslexia, which occurs in 5-17% of children, is a persistent difficulty in learning to read that is not explained by sensory deficits, cognitive deficits, lack of motivation, or lack of adequate reading instruction (1). Approximately one-fifth of individuals with developmental dyslexia manage to compensate for their underlying learning difficulties and develop adequate reading skills by the time they reach adulthood (2), but the mechanisms by which this compensation occurs remain largely unknown. Improved reading observed in developmental dyslexia is rarely complete, but instead refers to a level of reading superior to clinical cutoff scores that closes the gap between poor reader and typical readers, and that allows children to read adequately for purposes of learning. Many factors likely influence whether dyslexic children make substantial progress in reading, including access to educational resources and interventions, and neuropsychological and behavioral characteristics (reviewed in refs. 3 and 4), such as whether children have multiple deficits (e.g., in both rapid naming and phonological processing; ref. 5). A number of studies have examined neuropsychological, behavioral, and demographic predictors of developing dyslexia (e.g., refs. 6-8) and short-term response to intervention (RTI) (3, 4), but there is little evidence...

Individual Differences in Adult Reading Are Associated with Left Temporo-parietal to Dorsal Striatal Functional Connectivity

“…Increased activation in less skilled readers has been attributed to overengagement, due to increased difficulty and effort necessary during reading tasks (Shaywitz et al 1998;Brunswick et al 1999;Milne et al 2002). This compensatory theory is supported by findings of more prominent hyperactivation in older, or remediated, readers (Shaywitz et al 2003;Hoeft et al 2011;Richlan et al 2011;Barquero et al 2014).…”

Literacy after cerebral hemispherectomy: Can the isolated right hemisphere read?

“…that the RH is utilized by populations having reading deficits raises the question of whether the role of RH is only compensatory or whether it can independently support reading on its own when the LH is not available [9,40]. The findings of previous research that has investigated these questions (with a total of 7 patients across all these published studies) suggest heterogeneity in reading abilities following left hemispherectomy [19,20,[22][23][24].…”

“…Although language competence of the RH is now widely recognized [7], its involvement in reading in healthy populations is traditionally thought to be limited to higher-order skills, such as pragmatics, nonliteral language, and prosody, in addition to some role in semantic interpretation at the single-word level. Interestingly, imaging studies have suggested an increased involvement of the RH in struggling readers -including both those with developmental deficits (e.g., dyslexia) and those having acquired abnormalities (e.g., poststroke) on the left side [8][9][10][11][12][13]. The compensatory nature of RH involvement in these readers and an understanding of what possible advantages it offers for reading recovery remain unclear partly because of a lack of information regarding the potential of the isolated RH in the development of phonological processing and reading skills.…”

Functional characteristics of developmental dyslexia in left-hemispheric posterior brain regions predate reading onset

“…44, 50, and 64). Furthermore, it has been shown that right prefrontal activation in children with a diagnosis of DD can significantly predict reading gains 2.5-y later, indicating that these compensatory mechanisms can function as part of the reading network (64).…”