Working memory in children with Tourette syndrome (TS): Dual task performance and sentence comprehension

An influential model of working memory (Baddeley, 1994) was used as a conceptual framework for testing the neurological dopamine hypothesis of Tourette Syndrome (TS) that predicts dysfunctions of the prefrontal cortex. We administered a variety of screening measures as well as tests of dual task performance to children with TS (N = 40, 6 females) and age, sex and IQ matched controls. Parent ratings of TS children (Child Behaviour Check List) indicated many more problems and particularly with the Attention scale, than equivalent ratings by control group parents. Standardised tests purported to measure frontal lobe functioning (Wisconsin Card Sort Test, Tower of London), and specific tests of dual task perfor-mance (TEA-Ch, Visual Tracking and Memory Span Test), were of primary interest. The results indicated no group differences on the Wisconsin Card Sort or Tower of London tests. In the dual task measures, however, children with TS counted fewer spaceship blasts (in either condition of the TEA-Ch) and had reduced digit span in dual task conditions. Dual task decrement was found to be greater when the two tasks were conducted in the same modality, than when they were conducted in different modalities. For verbal memory, TS children showed poorer immediate recall of five common words and took longer to name pictures than controls. In terms of the model, impaired functioning of the phonological loop and the central executive control loop are implicated in TS rather than a generalised deficit of the central executive. Since attention deficit hyperactivity disorder frequently cooccurs with TS, further work is required to determine whether these impairments are TS specific