Pratt, Polly Louise; (2000) Executive functioning and habit learning in children with Tourette Syndrome. Doctoral thesis (D.Clin.Psy), UCL (University College London).

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Abstract

Research suggests that individuals with Tourette Syndrome (TS) have impaired fronto-striatal neural systems. This study aimed to examine the performance of children with TS on a range of neuropsychological measures that are thought to involve the activation of fronto-striatal structures. Participants were twenty children with TS and twenty healthy children to act as a Control group, matched for age, sex and IQ. Data was also collected on symptomatology, including tic severity, symptoms of obsessive compulsive disorder (OCD) and attention deficit hyperactivity disorder (ADHD), social skills and childhood problems. The main findings of the study were that the TS group performed significantly worse than the Control group on most of the tests of executive functioning used in the study. They were also impaired on the more sensitive tests of explicit memory used, which are thought to have an executive contribution. These results are consistent with existing research. There were no differences on tests of naming and perception, which are thought to be less reliant on executive skills. There were no significant differences between the groups on the priming and skill learning implicit tasks. Unfortunately, no studies of TS and implicit learning exist with which to compare this finding. There were few significant associations between symptomatology measures and performance on tests. In order to explore the significant differences further, the TS group was divided into two subgroups, those with only TS and those with the comorbid conditions of OCD, ADHD or both. The co-morbid group performed significantly worse than the group with only TS on the explicit memory tests, but on only two of the six executive measures. Therefore, TS symptomatology itself appears to account for the many of the differences between the TS group and the Control group on executive measures. The findings of this study suggest that the TS group were impaired on a range of executive measures. The lack of significant findings on the implicit learning measures suggests that habit-learning is intact. Consequently, it may be that executive problems account for the persistence of tics, in that once the tics are acquired they cannot properly be extinguished because the ability to inhibit responses is impaired. The implications for clinical interventions are considered on the basis of these findings.

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