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S. Trauzettel-Klosinski, K. Stingl, C. Hofmann, J. Wolf, D. Wildgruber, A. N. Sokolov, C. Braun; Reading Strategies During Processing of Known and Unknown Scripts in Patients With Developmental Dyslexia and Controls - Assessed by Magnetoencephalography. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1450.
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© ARVO (1962-2015); The Authors (2016-present)
In order to test whether there are two different paths of letter processing in dyslexics and controls we studied magnetic brain responses using whole-head magnetoencephalography during reading of a well trained and a newly acquired artificial script in dyslexics and controls.
Brain activity during word reading was studied in 10 dyslexics and 13 controls after learning a new script. In the new script, letters were replaced by Cyrillic and Greek like letters. Subjects trained the new alphabet for one week using a computer program. After training, participants read words written in both Latin and the new script in two subsequent blocks. In order to compare brain responses global brain activity was calculated. Furthermore, differences in cortical activation patterns were inferred by topographical analysis.
Analysis of the global brain activity revealed that brain processes at a latency of 250 ms after word presentation were delayed in the dyslexics with respect to controls during reading of words written both in Latin and the new script. Furthermore, the strength of activation as well as the topographical pattern of the sustained activation in the latency range from 350 ms to 500 ms with a maximum at around 470 ms differed significantly for control subjects reading Latin written words from reading the new script. No differences were found for the different scripts within the dyslexics as well as between dyslexics and controls reading words written in the new script.
Our data confirm previous findings of impairments in early grapheme processing. Furthermore, we conclude that efficient word reading relies on brain processes in temporal cortex that require intensive training and that are not accessible by dyslexics even during reading of well trained letters.
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