Dyslexia is a specific learning disorder that effects how someone understands words, writing, sounds. It is the most common learning disability, effecting of individuals. Symptoms may range from mild to severe. It is characterized by difficulties with accurate and/or fluent word recognition and by poor spelling and decoding abilities (shaywitz 2005). Developmental dyslexia effects around 5 -10 percent of children whom are otherwise of normal intelligence and show an impairment to reading despite adequate instruction (shaywitz 1998).
There is no single known cause of dyslexia. Researchers believe there are multiple biological and environmental factors that contribute to a diagnosis of dyslexia, yet the causes of dyslexia are not fully understood.
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Researchers used functional MRI to study brain activation as pseudowords and real words were read to children. 144 right handed children were used in the study. It was found that non dyslexic children demonstrate significantly greater activation that do dyslexic children in left hemisphere sites including the the inferior frontal, superior temporal, parietao-temporal and middle temporal-middle occipital gyri and right hemisphere sites including an anterior site around the inferior frontal gyrus and two posterior sites, one in the parieto-temporal region, the other in the occipito-temporal region(shaywitz 2008). This study supports previous studies that have shown a failure of left hemisphere posterior brain activation during reading in dyslexic individuals(shaywitz 2008). Due to findings that show abnormalities in both posterior and anterior language networks, researchers have hypothesized that dyslexia is a disconnection …show more content…
Findings have found local white matter changes in children and adults with dyslexia in the left tempopartietal regions and in the left inferior front gyrus(deutsch 2005, klingberg 2000). Using diffusion tensor imaging(DTI), antisotrophy values of adults with poor reading skills and developmental reading disorders were compared to anisotrophy values of control adults with no history of reading disorders. The results showed that in two bilateral regions in the temporo-parietal region of the brain, there were lower anisotrophy levels in the poor readers. These results indicated that white matter within the temporo-parietal cortex plays a crucial role in the ability to read (klingberg 2000). Studies have consistently reported correlations between white matter integrity and phonological skills (annual review). Klingberg conducted study that linked a genetic association with white matter, which correlated with previous research that proposed a link beween DYXICi, DCDC2, and KIAA0319. Since these genes have been found to increase risk of dyslexia, it seems that these genes are altering brain development in the left hemisphere which is important for language development, and thus hindering written language acquisition. More research is still needed, but this study opens up more questions on how genes are related to