Visual event-related potentials in children with phenylketonuria

Visual event-related potentials (ERPs) were examined in 16 children (aged 5 -14 y) with phenylketonuria (PKU) and 16 age- and sex-matched controls. Lif etime median measures of phenylalanine (Phe) were 230-460 mu mol/l. The mos t recent Phe levels were 56-624 mu mol/l. ERPs were recorded whilst the chi ldren performed a discrimination task. All stimuli were square wave grating s degree, which appeared for 33 ms. A response to an infrequent grating tha t differed in orientation or spatial frequency was required. The older chil dren with PKU had a delay in the first peak (P1) of the ERP, and age-relate d changes in the amplitude of P1. There was attenuation of the second peak across age groups in PKU. There was no evidence of reduced response accurac y or longer reaction times in children with PKU, Latencies of the cognitive P3 were not delayed in PKU. The delayed early peaks are consistent with pr evious studies that have shown delayed visual evoked potentials in PKU. The lack of differences in reaction time and P3 may be due to relatively good Phe control in children with PKU, or to the simplicity of the task. Suggest ions are made for future ERP studies of PKU.