Pressing and tapping movements (see Movement tasks) were recorded by a custom-made device consisting of a force transducer and two photoelectric beam sensors (Fig. 1A). The digital signal from the force transducer was used to define the peripheral time of movement onset and offset of the pressing task. For that task, the peripheral movement onset and offset of pressing were defined as the moments when the force exceeded or fell below a threshold of 1.3 N, respectively. A threshold of 1.3 N was empirically derived from pilot studies. This threshold was chosen such that it reliably fell into the interval between the force values at rest and constant pressure for all subjects. The maximum force that the transducer could detect was 4.4 N.
