We evaluated signal-noise discrimination in children with and without dyslexia, using
magnocellular and parvocellular visual stimuli presented either with or without high noise.
Dyslexic children had elevated contrast thresholds when stimuli of either type were
presented in high noise, but performed as well as non-dyslexic children when either type
was displayed without noise. Our findings suggest that deficits in noise exclusion, not
magnocellular processing, contribute to the etiology of dyslexia.