Developmental dyslexia: passive visual stimulation provides no evidence for a magnocellular processing defect.
Livingstone et al. [Livingstone, M. S., Rosen, G. D., Drislane, F. W. and Galaburda, A. M. Physiological and anatomical evidence for a magnocellular defect in developmental dyslexia. Proceedings of the National Academy of Science U.S.A. 88, 7943-7947, 1991] presented evidence for a defect of the magnocellular visual processing stream in developmental dyslexia. We attempted to replicate this effect using transient and steady-state VEPs to checkerboard reversal stimuli in a group of adult developmental dyslexics. Several different reversal rates and contract levels were utilized. No differences were found between the dyslexic and control groups for the low-contrast, rapidly reversing patterns, nor for any combination of stimulus rate or contrast that was tested. Thus, these findings do not support a magnocellular processing deficit in developmental dyslexia.
Department of Neurology, Medical School of Hannover, Germany. johannes@vm.mhrz.mh-hannover.de
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Johannes
C L
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Kussmaul
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Münte
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Mangun
D000328:Adult; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000503:physiopathology; D004410:Dyslexia / Q000175:diagnosis / Q000503:physiopathology*; D004569:Electroencephalography; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005260:Female; D005829:Geniculate Bodies / Q000503:physiopathology*; D006801:Humans; D008297:Male; D010775:Photic Stimulation; D011930:Reaction Time / Q000502:physiology; D014795:Visual Pathways / Q000503:physiopathology*; D014796:Visual Perception / Q000502:physiology*