title: Eliciting dyslexic symptoms in proficient readers by simulating deficits in grapheme-to-phoneme conversion and visuo-magnocellular processing.
abstract: Among the cognitive causes of dyslexia, phonological and magnocellular deficits have attracted a substantial amount of research. Their role and their exact impact on reading ability are still a matter of debate, partly also because large samples of dyslexics are hard to recruit. Here, we report a new technique to simulate dyslexic symptoms in normal readers in two ways. Although difficulties in grapheme-to-phoneme conversion were elicited by manipulating the identifiability of written letters, visual-magnocellular processing deficits were generated by presenting letters moving dynamically on the screen. Both factors were embedded into a lexical word-pseudoword decision task with proficient German readers. Although both experimental variations systematically increased lexical decision times, they did not interact. Subjects successfully performed word-pseudoword distinctions at all levels of simulation, with consistently longer reaction times for pseudowords than for words. Interestingly, detecting a pseudoword was more difficult in the grapheme-to-phoneme conversion simulation as indicated by a significant interaction of word type and letter shape. These behavioural effects are consistent with those observed in 'real' dyslexics in the literature. The paradigm is thus a potential means of generating novel hypotheses about dyslexia, which can easily be tested with normal readers before screening and recruiting real dyslexics.
authors.affiliation: Research Centre Jülich, Institute of Neurosciences and Medicine (INM-1 and INM-3), Germany.
authors.forename: Nicole
authors.initials: N
authors.lastname: Tholen
authors.forename: Ralph
authors.initials: R
authors.lastname: Weidner
authors.forename: Marion
authors.initials: M
authors.lastname: Grande
authors.forename: Katrin
authors.initials: K
authors.lastname: Amunts
authors.forename: Stefan
authors.initials: S
authors.lastname: Heim
mesh_terms: D000328:Adult; D001364:Awareness; D003198:Computer Simulation; D003657:Decision Making; D004410:Dyslexia / Q000209:etiology*; D005260:Female; D006801:Humans; D007807:Language Tests; D008297:Male; D008875:Middle Aged; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010468:Perceptual Disorders / Q000150:complications*; D010700:Phonetics; D010775:Photic Stimulation; D011582:Psychological Theory; D011930:Reaction Time / Q000502:physiology; D014793:Visual Cortex / Q000503:physiopathology; D014795:Visual Pathways; D014825:Vocabulary; D055815:Young Adult