Temporal discrimination of cross-modal and unimodal stimuli in generalized dystonia

Motor and nonmotor timing functions and cross-modal processing of visual-tactile signals may be linked to basal ganglia. These neural structures are thought to be dysfunctional in dystonia.

To test whether cross-modal stimulation influences deficits of temporal discrimination in dystonia.

Eight patients with generalized dystonia and 10 control subjects were asked to discriminate whether pairs of unimodal (tactile or visual) and cross-modal (visual and tactile) stimuli were simultaneous or sequential and, in the latter case, which stimulus preceded the other. Visual stimuli consisted of red lights and tactile stimuli of non-noxious electrical shocks. Intervals between stimuli in each pair were increased from 0 to 400 msec (in steps of 10 msec).

Patients with dystonia recognized the asynchrony between the experimental stimuli and judged correctly which stimulus in a pair came first, at significantly longer intervals than did controls. Moreover, differences in performance between patients and controls were maximal for cross-modal stimuli. The defective performance of patients with dystonia in the cross-modal combinations showed a high positive correlation with the severity of symptoms.

Patients with generalized dystonia present with difficulties both in timing functions and in cross-modal processing of visual-tactile stimuli.