Neuropsychological and cognitive correlates in Tourette Syndrome. The inhibitory process hypothesis

Objective: Tourette Syndrome involves involuntary movements known as tics, which can enable the subject to make good performances in cognitive tasks. Spatial memory and selective attention appear to be impaired in subjects with TS, as revealed by behavioural and ERP correlates. The present study intends to explore the congitive and neuropsychological performance of a patient with TS. Participants and Methods: Two cognitive tasks (Spatial Memory and Stroop Test) have been presented to a female subject with Tourette Syndrome, Plus category, during the registration of psychophysiological parameters (autonomic measures) and EEG profile (ERP procedure). Behavioral (correct responses), psychophysiological (EDA, Blood Pressure, Heart Rate), and EEG indexes (ERP effects) were monitored during the two task execution. Results: The subject has shown an adequate level of behavioural performances, as well as a functional arousal response related to the cognitive tasks. Nevertheless, the first phase of Spatial Memory task (coding) elicitated an increased frontal P300a and a parietal P300b effect, while the second phase (response behaviour) activated N200 peak deflection higher on the parietal sites. Secondly, Stroop elicited a higher N200 peak in response to congruous targets within the parietal and occipital sites. Conclusions: These results are compatible with the inhibitory hypothesis, which states the presence of a iper-functional control adopted by the subjects in order to check for the tic behaviour. Moreover, according to previous works (Smith, 2004; Johannes, 2003) attentive task could have activated an inhibitory process triggered by that TS patients, finalyzed to have a good performance.