Perceptual differences in sequential stimuli across patients with musician's and writer's cramp.

Previous research has demonstrated a relationship between the regularity of motor production and the ability to make accurate perceptual judgments. The current study investigated the temporal abilities of two groups of patients with known movement problems (musicians' and writers' cramp), some of whom have had many years of training in temporal discrimination. Patients and controls (musician and nonmusician, respectively) judged whether the last of six sequential auditory or tactile stimuli occurred earlier or later in comparison to five previously and regularly presented stimuli. In both sensory domains, patients with musicians' cramp detected the early stimulus better than controls. When detecting the onset of late stimuli, only in the auditory domain were patients worse than controls. Patients with writers' cramp, however, did not show any significant group differences in either auditory or tactile domains, suggesting that such patients are not deficient in processing sequential stimuli. In conclusion, compared to controls, patients with musician's cramp demonstrated generalized timing anomalies, occurring in the symptomatic (tactile) and the asymptomatic (auditory) sensory domains. This timing problem is likely to be a consequence of the dystonic symptoms rather than the cause.