BRAIN ACTIVITY IN VISUAL-CORTEX PREDICTS INDIVIDUAL-DIFFERENCES IN READING PERFORMANCE

The relationship between brain activity and reading performance was ex amined to test the hypothesis that dyslexia involves a deficit in a sp ecific visual pathway known as the magnocellular (M) pathway. Function al magnetic resonance imaging was used to measure brain activity in dy slexic and control subjects in conditions designed to preferentially s timulate the M pathway. Dyslexics showed reduced activity compared wit h controls both in the primary visual cortex and in a secondary cortic al visual area (MT+) that is believed to receive a strong M pathway in put. Most importantly, significant correlations were found between ind ividual differences in reading rate and brain activity. These results support the hypothesis for an M pathway abnormality in dyslexia and im ply a strong relationship between the integrity of the M pathway and r eading ability.