NORMAL ACTIVATION OF FRONTOTEMPORAL LANGUAGE CORTEX IN DYSLEXIA, AS MEASURED WITH O-15 POSITRON EMISSION TOMOGRAPHY

Objective: To assess the ability of dyslexic men to activate left midd le to anterior language cortex normally. Design: Positron emission tom ography using oxygen 15-labeled water as a tracer during rest and duri ng a syntax task involving sentence comprehension. Setting: Research h ospital. Patients or Other Participants: Fifteen right-handed, severel y dyslexic men (mean [+/-SD] age, 27+/-5 years) and 20 matched control s. Interventions: None. Main Outcome Measure: Cerebral blood flow. Res ults: During rest, dyslexics showed reduced blood flow (relative to co ntrols) in one left parietal region near the angular/supramarginal gyr i, but otherwise normal flow. During syntactic processing, dyslexics a nd controls showed similar, significant activation of left middle to a nterior temporal and inferior frontal cortex. Conclusions: These resul ts, together with the previously reported failure of dyslexics to acti vate left temporoparietal cortex during phonologic processing, argue f or dysfunction of left cortical language areas restricted to posterior language regions in dyslexia.