Testverfah - Bundesverband Legasthenie und Dyskalkulie eV

Abstractband 15. Kongress des Bundesverbandes Legasthenie
Neurobiology of dyslexia: a new perspective
*Franck Ramus
Laboratoire de Sciences Cognitives et Psycholinguistique Ecole Normale Supérieure, Ecole Normale
Supérieure, Paris, Frankreich
Theories of developmental dyslexia differ on how to best interpret the great variety
of symptoms (linguistic, sensory, motor) observed in dyslexic individuals. One approach
views dyslexia as a specific phonological deficit, which sometimes co-occurs
with a more general sensorimotor syndrome. I will review the neurobiology of
dyslexia and show that neurobiological data are indeed consistent with this view,
explaining both how a specific phonological deficit might arise, and why a sensorimotor
syndrome should be significantly associated with it. This new conceptualisation
of the aetiology of dyslexia may generalise to other neuro-developmental disorders,
and may further explain heterogeneity within each disorder and co-morbidity between
disorders.
Korrespondenzautor:
Franck Ramus
franck.ramus@ens.fr
++33 1 44322356
++33 1 44322360
Dyslexia susceptibility genes on chromosome 2q
*Wendy Raskind
University of Washington, Department of Medicine, Washington, Vereinigte Staaten
von Amerika
Impaired phonological decoding is one of the core deficits of dyslexia. In families ascertained
in the UW LDC through a school-aged child with dyslexia, impairments in
rate of phonological decoding remained stable from childhood to adulthood, despite
varying degrees of compensation for reading text. We performed a genome scan
of two continuous measures of phonological decoding ability: phonemic decoding
efficiency (PDE), a measure of both accuracy and speed, and word attack (WA), a
measure of accuracy alone. Multipoint variance component linkage analyses (VC)
and Markov chain Monte-Carlo (MCMC) multipoint joint linkage and segregation
analyses on 108 pedigrees revealed a strong signal on chromosome 2 for PDE (VC-
LOD=2.65 and intensity ratio (IR)=32.1). The IR is an estimate of the ratio of the
posterior to prior probability of linkage in MCMC analysis. This chromosome 2 signal
was not seen for WA. More detailed mapping with additional markers provided statistically
significant evidence for linkage of PDE to chromosome 2, with VC-LOD=3.0
and IR=59.6 at D2S1399. The multipoint VC-LOD score corresponds to a theoretical
p value of 0.0001. Parametric analyses, using a model obtained by complex
segregation analysis, provided a multipoint maximum LOD=2.89. The consistency
of results from three analytic approaches provides strong evidence for a locus on
chromosome 2q that influences speed but not accuracy of phonological decoding.
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