Executive function in treated phenylketonuria as measured by the one-back and two-back versions of the continuous performance test.

[classical phenylketonuria]

The executive dysfunction hypothesis in treated phenylketonuria was investigated by means of the one -back and two -back versions of the continuous performance test . Eleven non-retarded , primary school -age children with classical phenylketonuria who had been treated early and continuously were indistinguishable from healthy , matched controls on the measures and test performance was not predicted by historical or concurrent plasma phenylalanine concentrations . Mean lifetime phenylalanine concentrations for the phenylketonuric subjects were within ranges currently recommended as dietary optima in the United Kingdom . The negative neuropsychological test findings add weight to the rationale for this policy .