Developmental dyslexia: Passive visual stimulation provides no evidence for a magnocellular processing defect

• Published in: Neuropsychologia 1996-11, Vol.34 (11), p.1123-1127
• Main Authors: Johannes, Sönke, Kussmaul, Clifton L., Münte, Thomas F., Mangun, George R.
• Format: Article
• Language: English
• Subjects: Adult; Brain Mapping; Cerebral Cortex - physiopathology; developmental dyslexia; Dyslexia - diagnosis; Dyslexia - physiopathology; Electroencephalography; Evoked Potentials, Visual - physiology; Female; Geniculate Bodies - physiopathology; human; Humans; magnocellular pathway; Male; Photic Stimulation; Reaction Time - physiology; Space life sciences; visual evoked potentials (VEP); Visual Pathways - physiopathology; Visual Perception - physiology
• ISSN: 0028-3932; 1873-3514
• DOI: 10.1016/0028-3932(96)00026-7

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. They reported diminished visual evoked potentials (VEP) to low-contrast, rapid checkerboard reversal patterns in the dyslexics. 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 contrast 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.