In the tapping tasks, we applied a two-way mixed ANOVA with the factors group and feedback on the three performance parameters (tapping rate, tapping variability, and completion ratio), as shown in Table 1. In slow tapping, the tapping rate was slightly higher in patients (mean rate: 1.01 ± 0.35/s) than in controls (mean rate: 0.80 ± 0.23/s, Fig. 2Bi). Rate increased in both groups with visual feedback, probably through an effect of pacing by the visual feedback (Table 1). The tapping variability was affected neither by group nor by feedback (Table 1). Regarding the mean completion ratio, which indicates the mean percentage of taps reaching the amplitude criterion in a task, we found a significant interaction effect between group and feedback (Table 1). Post hoc testing (Fig. 2Bii) revealed no significant differences between groups, although the completion ratio increased with visual feedback only in patients. More interestingly, the EMG slope at tapping onset (index finger extension) was significantly lower in patients compared with controls (Fig. 2Biii).
