Speed of processing and executive functions in adults with phenylketonuria: Quick in finding the word, but not the ladybird

• Published in: Cognitive neuropsychology Vol. 35; no. 3-4; pp. 171 - 198
• Main Authors: Romani, Cristina, MacDonald, Anita, De Felice, Sara, Palermo, Liana
• Format: Journal Article
• Language: English
• Published: England 19-05-2018
• Subjects: Phenylketonuria; ageing; feature vs. conjunction search; executive functions; serial vs. parallel search; speed of processing
• ISSN: 0264-3294; 1464-0627
• DOI: 10.1080/02643294.2017.1320278

A reduction in processing speed is widely reported in phenylketonuria (PKU), possibly due to white matter pathology. We investigated possible deficits and their relationships with executive functions in a sample of 37 early-treated adults with PKU (AwPKUs). AwPKUs were not characterized by a generalized speed deficit, but instead their performance could be explained by two more specific impairments: (a) a deficit in the allocation of visuo-spatial attention that reduced speed in visual search tasks, in some reading conditions and visuo-motor coordination tasks; and (b) a more conservative decision mechanism that slowed down returning an answer across domains. These results suggest that the impairments in executive functions seen in AwPKUs are not the consequence of a generalized speed deficit. They also suggest that processing speed is linked to the efficiency of a particular cognitive component and cannot be considered a general function spanning domains. Similarities with patterns in ageing are discussed.