Language processing and executive functions in early treated adults with phenylketonuria (PKU)

ABSTRACT

We provide an in-depth analysis of language functions in early-treated adults with phenylketonuria (AwPKUs, N = 15–33), as compared to age- and education-matched controls (N = 24–32; N varying across tasks), through: a. narrative production (the Cinderella story), b. language pragmatics comprehension (humour, metaphors, inferred meaning), c. prosody discrimination d. lexical inhibitory control and planning (Blocked Cyclic Naming; Hayling Sentence Completion Test, Burgess & Shallice, 1997). AwPKUs exhibited intact basic language processing (lexical retrieval, phonology/articulation, sentence construction). Instead, deficits emerged in planning and reasoning abilities. Compared to controls, AwPKUs were: less informative in narrative production (lower rate of Correct Information Units); slower in metaphorical understanding and inferred meaning; less accurate in focused lexical-search (Hayling test). These results suggest that i) executive deficits in PKU cannot be explained by an accumulation of lower-order deficits and/or general speed impairments, ii) executive functions engage dedicated neurophysiological resources, rather than simply being an emergent property of lower-level systems.

KEYWORDS:

• Executive Functions
• Speed of Processing
• Language pragmatics
• Phenylketonuria
• Metabolic Disorders

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

1 Note, however, that one of these participants arrived in the UK as teenager. However, he had very good English and attended university. Moreover, our results are in z-scores from controls, which always included an individual with a similar history. All other participants had always resided in the UK.

Additional information

Funding

This research was supported by a Marie Curie Intra European Fellowship within the 7th European Community Framework Programme granted to Liana Palermo under the supervision of Cristina Romani (grant number 329423) and by a grant of the University Hospital Birmingham Charity to Tarekegn Gerberhiwot.