Investigating the functional integrity of the dorsal visual pathway in autism and dyslexia

Numerous reports of elevated global motion thresholds across a variety of neurodevelopmental disorders have prompted researchers to suggest that abnormalities in global motion perception are a result of a general deficiency in the dorsal visual pathway. To test this hypothesis, we assessed the integrity of the dorsal visual pathway at lower subcortical (sensitivity to flicker contrast) and higher cortical (sensitivity to global motion) levels in children with autism, children with dyslexia, and typically developing children, of similar age and ability. While children with autism demonstrated intact lower-level, but impaired higher-level dorsal-stream functioning, children with dyslexia displayed abnormalities at both lower and higher levels of the dorsal visual stream. These findings suggest that these disorders can be dissociated according to the origin of the impairment along the dorsal-stream pathway. Implications for general cross-syndrome accounts are discussed.