Event-related potential correlates of selective processing in early- and continuously-treated children with phenylketonuria: effects of concurrent phenylalanine level and dietary control.

This study focused on important characteristics of attentional (selective) processing in children with early-treated phenylketonuria (PKU). Seven to 14-year-old children with PKU were allocated to high phenylalanine (Phe) and low Phe groups and compared with control children on amplitudes and latencies of early and late event-related potential (ERP) components elicited during a selective processing task. These components are thought to measure early sensory processes (stimulus encoding/perception) and later selection processes (target detection). The effects of concurrent Phe level and dietary control on brain activity and behavioural performance were studied. Results showed that children with PKU with high Phe levels were less accurate and made more false alarms than controls and children with PKU with low Phe levels. Both children with PKU and controls displayed the expected early fronto-central selection negativity and a late positive peak over posterior sites associated with sensory aspects of the selective attention task. However, in contrast with controls, children with PKU showed an absence of condition differences for selection positivity over anterior sites associated with target detection. Negative and positive selection potentials over fronto-central sites were dependent on concurrent and historical Phe levels, whereas sensory potentials depended more strongly on historical Phe levels. It is concluded that both sensory and selection aspects of attention are affected by Phe levels. The relative predictive strength of historical Phe levels suggests that high Phe levels during sensitive periods for brain maturation may have long-lasting influences on selective attention.