Few researchers agree about the relationship between fronto–temporo–parietal white matter microstructure and reading skills. Unlike many previous reports, which only measured fractional anisotropy, we have also measured macroscopic volume (regional white matter tract volume) and three microstructural indices (axial, radial, and mean diffusivity) to increase interpretability of our findings. We examined the reading‐related skills and white matter structure in 10 adolescents and adults with a history of poor reading and 20 age‐matched typical readers. We applied a diffusion tensor imaging atlas‐based algorithm to major white matter pathways. The relation of white matter structural indices to reading group, hemisphere, and reading‐related skill was analyzed using linear models. White matter microstructural indices were related to performance on a sublexical decoding task, but the relations between particular microstructural indices and sublexical decoding ability and reading group were different for association (i.e., cortical–cortical) and projection (i.e., subcortical–cortical) white matter pathways. Changes in projection pathways were consistent with alterations in white matter organization and axonal size, whereas changes in association pathways were consistent with alternations in pathway complexity. Changes in macrostructure paralleled changes in microstructure. We conclude that the relations between several microstructural indices and factors related to reading ability are different for association and projection pathways. Hum Brain Mapp, 2011. © 2010 Wiley‐Liss, Inc.

Abstract Although supportive parenting has been shown to have positive effects on development, the neurobiological basis of supportive parenting has not been investigated. Thirty-three adolescents were systemically selected from a longitudinal study on child development based on maternal responsiveness during childhood, a measure of supportive parenting, and whether they were born term or preterm. We analyzed the effect of preterm birth on hemispheric and regional (frontal, temporal, parietal) cortical thickness and surface area using mixed-model analysis while also considering the effect of brain hemisphere (left vs. right). We then determined whether these factors were moderated by maternal responsiveness during childhood. Preterm birth was associated with regional and hemispheric differences in cortical thickness and surface area. Maternal responsiveness during childhood moderated hemispheric cortical thickness. Adolescence with mothers that were inconsistently responsive during childhood demonstrated greater overall cortical thickness and greater asymmetry in cortical thickness during adolescence as compared to adolescence with mothers who were consistently responsive or unresponsive during childhood. Maternal responsiveness and preterm birth did not interact. These data suggest that changes in brain morphology associated with preterm birth continue into adolescence and support the notion that the style of maternal-child interactions during childhood influence brain development into adolescence. (JINS, 2010, 16, 784–794.)

AimTo understand the relationship between cognition and white-matter structure in adolescents born preterm without obvious brain injury.MethodsThirty-two adolescents from a longitudinal study of child development were selected according to risk of developmental disorders at birth (born at term: eight males, five females; median age 16y 1mo, interquartile range 10mo; low risk preterm: four males, five females, median age 16y, range 4mo; high risk preterm: three males, seven females, median age 16y 2mo, range 1y 2mo) and reading ability (good: three males, eight females, median age 16y, range 7mo; average: six males, three females, median age 16y 10mo, range 1y; poor: six males, six females, median age 16y, range 6mo). Preterm birth was defined as a gestational age of 36 weeks or less and a birthweight of 1600g or less. All participants had normal clinical neuroimaging findings. We examined fractional anisotropy, radial diffusivity, and volume of three major white-matter fasciculi. The relationship between structural measures and birth risk, hemisphere, and cognitive ability (attention, lexical and sublexical decoding, auditory phonological awareness, and processing speed) were analysed using mixed-model regression.ResultsLeft-hemisphere superior longitudinal fasciculus (SLF) fractional anisotropy and radial diffusivity were linked to reading-related skills (fractional anisotropy vs letter-word identification, r((30))=-0.37, p < 0.05; fractional anisotropy vs phoneme reversal, r((30))=-0.34, p=0.05; radial diffusivity vs letter-word identification, r((30))=0.31, p < 0.10; radial diffusivity vs phoneme reversal, r((30))=0.40, p < 0.05), whereas right-hemisphere SLF fractional anisotropy was related to attention skills (fractional anisotropy vs inattentiveness, r((30))=-0.38, p < 0.05). SLF volume decreased as these skills declined for adolescents born preterm (volume vs phoneme reversal, r((17))=0.58, p < 0.01; volume vs inattentiveness, r((17))=-0.69, p < 0.01), but not for those born at term.InterpretationThe relationship between cognitive skills and SLF volume suggests that in adolescents born preterm, cryptic white-matter injury may exist, possibly related to oligodendrocyte or axonal loss, despite normal clinical neuroimaging.

It is unknown whether the abnormalities in brain structure and function observed in dyslexic readers are congenital or arise later in development. Analyzing the 2 components of gray matter volume separately may help in differentiating these possibilities. Gray matter volume is the product of cortical surface area, determined during prenatal brain development, and cortical thickness, determined during postnatal development. For this study, 16 adults with a history of phonological dyslexia and 16 age- and gender-matched controls underwent magnetic resonance imaging and an extensive battery of tests of reading-related skills. Cortical surface area and gray matter volume measures of the whole brain, the inferior frontal gyrus, and the fusiform gyrus were similarly related to phonological skills and a history of dyslexia. There was no relationship between cortical thickness and phonological skills or history of dyslexia. Because cortical surface area reflects cortical folding patterns determined prenatally, this suggests that brain differences in dyslexia are rooted in early cortical development and are not due to compensatory changes that occur during postnatal development and would be expected to influence cortical thickness. This study demonstrates the importance of examining the separate components of gray matter volume when studying developmental abnormalities.

Although individuals born preterm are at risk for cognitive dysfunction, few studies have examined functional brain reorganization in these individuals. We used magnetoencephalography (MEG) to examine cortical reorganization related to preterm birth. Thirty-one adolescents systemically selected from a longitudinal study on child development based on gestational age, birth weight and medical complications (full term, low risk preterm, high-risk preterm) performed real-word and non-word auditory rhyme tasks during MEG recording. Equivalent current dipoles were localized every 4ms during the 50- to 250-ms period following the onset of the auditory stimulus. The association between the number of dipoles (NODs) and birth group, language task, latency and phonological skills was examined. Adolescents born preterm at high risk demonstrated a greater NODs in the left Broca's and prefrontal areas combined, left cingulate gyrus and left superior temporal gyrus and a fewer NODs in the right superior temporal gyrus as compared to those born preterm at low risk and term. A greater NODs in the left Broca's and prefrontal areas combined and fewer NODs in the left cingulate gyrus was associated with better phonological skills only in adolescents born preterm at high risk. These results suggest that the language networks are reorganized in adolescents born preterm at high risk. Increased prefrontal activity has also been seen in adolescents born preterm during a reading task and in young adults with a history of dyslexia who are well compensated for their disorder. We suggest that this increased prefrontal activation may represent increased top–down control of weak posterior language networks.

Inconsistent differences in the corpus callosum (CC) structure between dyslexic readers (DRs) and typical readers (TRs) have been reported. We examine differences in CC splenium microstructure and the association of splenium microstructure with reading-related skills. Nine DRs and 18 TRs completed a reading skills battery and diffusion tensor imaging. DRs had higher splenium fractional anisotropy (FA) and axial diffusivity (LA) as compared with TRs. Retrieval of orthographic information from the language lexicon was negatively associated with FA and LA within both reading groups. Phonological awareness was positively associated with splenium FA and LA in TRs but not DRs. This study suggests two white matter pathways that may be differentially associated with reading skills in the CC splenium.