Electrophysiological measures and dual-task performance in Tourette syndrome indicate deficient divided attention mechanisms

Tourette syndrome has been associated with impairments of attentional funct ions such as distractability, even in subjects without co-morbid attention deficit hyperactivity disorder. Based on the results of earlier research we hypothesized that Tourette syndrome patients might employ altered control mechanisms of attentional processes and have concurrent difficulties in all ocating their attentional resources among competing tasks. Event-related brain potentials (ERPs) were recorded in a group of Tourette syndrome patients and in a matched control group during a dual task experim ent. This experiment required the simultaneous detection of visual and audi tory target stimuli which were manipulated to yield two different difficult y levels each of which were varied orthogonally. The behavioural parameters confirmed the intended performance differences between difficult-to-detect targets and easy-to-detect targets. This was paralleled by lower amplitude s and longer latencies of the corresponding P3b-ERP subcomponents. Although Tourette syndrome patients were unimpaired in overall performance they sho wed an increased interference of visual task demands with auditory target p erception. In parallel they also exhibited a reduced amplitude of the P3b c omponent to auditory targets. The findings show that Tourette syndrome pati ents are not generally impaired in their dual task performance. The allocat ion of attentional resources to competing tasks however, is altered. We spe culate that this may be related to deficient inhibitory functions.