Dyslexia is a developmental disorder of the neurological system that results in a relatively selective impairment of an individual's ability to learn to read. It is described as an unexpected difficulty in learning to read in an individual who otherwise possesses the intelligence, motivation, and schooling considered necessary for accurate and fluent reading. Recent work continues to suggest that poor readers use more bilateral cortex during reading than do non-impaired readers, although the extent of differences between these groups in anatomical symmetry of brain regions that are important for reading remains unclear. Functional neuroimaging studies support long-held hypotheses that implicate both specific left-hemisphere language-related brain regions and an atypical pattern of right- versus left-hemisphere activity in the pathophysiology of dyslexia. Dyslexia is also associated with differences in neural activity in the left inferior frontal gyrus and in homologous right temporoparietal and right occipitotemporal junction areas, possibly to compensate for relative under activity in left posterior regions associated with phonological processing. Educational interventions, particularly those involving phonological training, are associated with improved reading skill and with changes in functional neuroimaging activation patterns toward those found in more skilled readers.
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