In this study, we examined the neuroanatomy of dyslexic (14 males, four females) and control (19 males, 13 females) children in grades 4-6 from a family genetics study. The dyslexics had specific deficits in word reading relative to the population mean and verbal IQ, but did not have primary language or motor deficits. Measurements of the posterior temporal lobe, inferior frontal gyrus, cerebellum and whole brain were collected from MRI scans. The dyslexics exhibited significantly smaller right anterior lobes of the cerebellum, pars triangularis bilaterally, and brain volume. Measures of the right cerebellar anterior lobe and the left and right pars triangularis correctly classified 72% of the dyslexic subjects (94% of whom had a rapid automatic naming deficit) and 88% of the controls. The cerebellar anterior lobe and pars triangularis made significant contributions to the classification of subjects after controlling for brain volume. Correlational analyses showed that these neuroanatomical measurements were also significantly correlated with reading, spelling and language measures related to dyslexia. Age was not related to any anatomical variable. Results for the dyslexic children from the family genetics study are discussed with reference to dyslexic adults from a prior study, who were ascertained on the basis of a discrepancy between phonological coding and reading comprehension. The volume of the right anterior lobe of the cerebellum distinguished dyslexic from control participants in both studies. The cerebellum is one of the most consistent locations for structural differences between dyslexic and control participants in imaging studies. This study may be the first to show that anomalies in a cerebellar-frontal circuit are associated with rapid automatic naming and the double-deficit subtype of dyslexia.

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These results suggest that behavioral gains from comprehensive reading instruction are associated with changes in brain function during performance of language tasks. Furthermore, these brain changes are specific to different language processes and closely resemble patterns of neural processing characteristic of normal readers.

A theory-driven battery of 23 psychometric measures of reading, writing, and related language processes was administered to 102 probands (affected children in Grades 1 to 6 with documented reading problems, writing problems, or both) and both of their biological parents. Affected children and parents were compared on the structural relationships between related language processes (Verbal IQ [VIQ], orthographic, phonological, and rapid naming skills), component reading, (accuracy, rate, comprehension) and writing (handwriting, spelling, composition) skills. The orthographic factor had significant paths to all reading and writing skills, except reading comprehension, in both probands and adults. The phonological factor had significant paths to all reading and writing skills except reading rate and handwriting in probands, but in affected adults only if VIQ was removed. Rapid naming had significant paths only to reading rate in probands and adults. VIQ had significant paths to reading comprehension in probands and adults, and to reading accuracy, reading rate, spelling, and composition in affected adults, but not probands. These results are consistent with the claim of functional systems theory that the same language processes are orchestrated flexibly depending on task at hand. Results for across-age differences in the covariances among related language processes confirmed developmental predictions of connectionist theory. The number of language deficits (based on discrepancy from SCIENTIFIC STUDIES OF READING, 5(1), 59-106

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