Edited By Evelin Witruk, Shally Novita, Yumi Lee and Dian Sari Utami
Evelin Witruk - Dyslexia – New Perspectives on an Old Phenomenon
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University of Leipzig, Germany
Dyslexia – New Perspectives on an Old Phenomenon
Abstract. The article aims to the question what is new until the last two decades in the dyslexia research and in the assessment. Some new aspects and some lines of progress will be discussed regarding the genetic basis of dyslexia, the hemispheric dominance, and the visual-spatial abilities of dyslexic individuals in different ages.
Keywords: genetic basis of dyslexia, hemispheric laterality, visual-spatial abilities.
1 From family and twin studies to the analysis of the genetic code
Family and twin studies indicated over decades a strong hereditary disposition of dyslexia. The studies showed that 40 % of the siblings and parents of a dyslexic were also having dyslexia (Grimm, 2001; Wilcke & Boltze, 2010). In twin studies, the genetic determination of dyslexia was highly estimated (about 60 %; Olson, Forsberg, & Wise, 1994). But the critical point regarding these studies is that the non-measured impact of family members, of cultural and natural environment were not be considered.
Linkage studies are a way to narrow the genomic region, where relevant disease genes are expected. Several genes have been linked to dyslexia, including DCDC2 and KIAA0319 on chromosome 6 and DYX1C1 on chromosome 15 (e. g., Grigorenko, et al., 1997). But, these findings are not always replicated. Molecular studies have linked several forms of dyslexia and different cognitive processes to genetic markers. However, no...
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