EXECUTIVE FUNCTION IN TREATED PHENYLKETONURIA AS MEASURED BY THE ONE-BACK AND 2-BACK VERSIONS OF THE CONTINUOUS PERFORMANCE-TEST

The executive dysfunction hypothesis in treated phenylketonuria was in vestigated by means of the one-back and two-back versions of the conti nuous performance test. Eleven non-retarded, primary school-age childr en with classical phenylketonuria who had been treated early and conti nuously were indistinguishable from healthy, matched controls on the m easures and test performance was not predicted by historical or concur rent plasma phenylalanine concentrations. Mean lifetime phenylalanine concentrations for the phenylketonuric subjects were within ranges cur rently recommended as dietary optima in the United Kingdom. The negati ve neuropsychological test findings add weight to the rationale for th is policy.