The decrement of tapping amplitude, as indexed by the decrease of completion ratio over a trial duration, was evaluated for tapping without visual feedback. We computed the mixed-effects model “completion ratio ∼ 1 + time bin + random(subjects),” separately for patients and controls. In slow tapping, the effect of time bin on the completion ratio was significant in patients, due to a decline over time [t(226) = −4.69, P < 0.001, FDR corrected] when 30-s epochs were used. The effect was no longer significant [t(226) = −1.58, P = 0.138, FDR corrected] when only considering the first 12 s of a trial, to facilitate comparison with the fast tapping task. Controls did not exhibit any decrement of amplitude in either case (data not shown). In fast tapping, evaluating the decrease of the completion ratio along the sequence of time points, we found a significant effect of time bin on the decrease of the completion ratio in the patients [t(226) = −5.45, P < 0.001, FDR corrected].
