Abstract: Gilles de la Tourette syndrome (TS) is a basal ganglia (BG)
disorder, associated not only with hyperkinetic movements but also with
attentional impairments. This experiment sought to ascertain whether overt
direct visual attention would influence tactile attentional performance in TS,
via the use of a vibrotactile choice reaction time procedure involving biased
probabilities of event occurrence. Participants were required to look (i.e.,
direct gaze) either at the hand receiving the most (expected) vibrations, or
the hand less often stimulated (the unexpected), for both crossed and uncrossed
arm postures. Contrary to our predictions, gaze did not influence
attentional performance in TS patients. Furthermore, patients were found
not to be sensitive to distributions of event probability; that is, they did
not demonstrate normal expectancy effects like controls. Attentional deficits
in TS (as in Parkinson's disease, another BG disorder) may pertain more to
difficulties in holding rather than in shifting the focus of attention.
Moreover, directing attention towards the unexpected locus in the crossed arm
posture improved overall performance in both patients and controls, suggesting
that increased task demands (e.g., crossed arm posture), and/or unexpected
stimulus location, may be alleviated by directed attention. These impairments
may stem from dysfunction in the circuits linking the frontal lobes with the
BG.
