Interhemispheric interaction during childhood: II. Children with early-treated phenylketonuria

This study examined whether children with early-treated phenylketonuria (ET PKU) exhibited a disruption in communication between the hemispheres as a f unction of computational complexity (Banich & Belger, 1990; Belger & Banich , 1992, 1998) when compared to neurologically uncompromised children who we re matched in age and IQ. This investigation was motivated by findings that phenylketonuria affects myelination of neurons, including those that make up the corpus callosum, the main neural conduit for interhemispheric intera ction. Children performed 2 tasks: a less complex physical-identity task an d a more complex name-identity task. For both tasks, we compared performanc e on across-hemisphere trials, which require interhemispheric interaction, and on within-hemisphere trials, in which no hemispheric interaction is req uired. On the more complex name-identity task, children with ETPKU exhibite d less of a benefit from across-hemisphere processing than did neurological ly intact children. These results suggest that the interhemispheric interac tion required to complete computationally complex tasks is compromised in c hildren with ETPKU. Such an insufficiency may explain some of the attention al deficits observed in this group of children.