Visual evoked potential evidence for magnocellular system deficit in dyslexia.
Some recent studies on dyslexia have suggested a selective abnormality in the magnocellular visual pathway. To verify this hypothesis, we investigated motion-onset visual evoked potentials (VEPs) (predominantly testing the magnocellular system) as well as pattern-reversal VEPs (presumably testing the parvocellular system) in 20 dyslexics and 16 controls (both groups with a mean age of 10.0 years). Although the latencies and amplitudes of the main positive peak of pattern-reversal VEPs did not differ between the dyslexic and control group, the motion specific negative peak of motion-onset VEPs was significantly delayed (p < 0.001) in dyslexics. Our results confirm a selective magnocellular pathway disorder in dyslexics and indicate that the motion-onset VEPs might serve as an objective method for early diagnosis of dyslexia.
Kubová
Z
Z
Department of Physiology, Charles University, Faculty of Medicine, Hradec Králové, Czech Republic.
Kuba
M
M
Peregrin
J
J
Nováková
V
V
D002648:Child; D004410:Dyslexia / Q000473:pathology / Q000503:physiopathology*; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009039:Motion Perception / Q000502:physiology; D010775:Photic Stimulation; D015349:Vision, Monocular / Q000502:physiology; D014795:Visual Pathways / Q000473:pathology / Q000503:physiopathology*