Temporal processing of visuotactile and tactile stimuli in writer's cramp

Neurophysiological studies in animals show that basal ganglia are involved not only in motor and nonmotor timing functions but also in integrating tactile and visual signals delivered in the peripersonal space. We tested temporal dis-crimination of cross-modal and unimodal stimuli in 13 controls and 14 patients with writer’s cramp, a disorder sup-posedly linked to dysfunction of basal ganglia. Subjects were asked to discriminate whether pairs of visual, tactile, or visuotactile stimuli were simultaneous or sequential (temporal discrimination threshold) and which stimulus preceded the other (temporal order judgment). Patients were impaired in temporal processing of tactile and cross-modal stimuli. A significant positive correlation between temporal deficits and the severity of disability was detected for both affected and unaffected sides. Findings suggest that multimodal and not only modality-specific temporal processing is defective in focal hand dystonia. Deficits of temporal processing of stimuli delivered to the unaffected side may represent a behav-ioral index of the susceptibility to develop dystonia and thus have remarkable practical and theoretical implications. Ann Neurol 2003;53:630–635 The term dystonia refers to a neurological syndrome supposedly linked to a dysfunction of basal ganglia and characterized by sustained muscular contractions that cause repetitive movements and abnormal postures