Regional cerebral blood flow correlates of language processes in reading disability.

This series of studies tests the hypothesis of abnormal left hemisphere activation in reading-disabled subjects during language task performance. First, a left superotemporal focus of activation, as measured by regional cerebral blood flow, was found to be positively correlated with task accuracy in a group of 69 normal adults. Next, that left superotemporal activation was replicated in a second group of 83 adults whose childhood reading ability was known from standardized tests given in childhood. Finally, in that latter group, childhood reading ability was also found to be inversely correlated with focal activation in a more posterior, temporoparietal area of cortex. Adult reading outcome was statistically unrelated to this finding. The results are interpreted as suggesting a trait anomaly of left hemisphere cerebral activation in adults who were dyslexic as children and as providing an existence proof of individual differences in focal cortical activation sites during constant task demands.