to rest, to minimize fatigue. Two different conditions (blocks) were designed for each of the tapping tasks (Fig. 1C). These conditions differed in the absence (FB-) or presence (FB+) of feedback as to whether the index finger extension had met the upper-level criterion, as detected by the upper photoelectric light beam (Fig. 1C). In FB+, subjects were instructed to increase their index finger’s height according to the feedback, if necessary. The feedback consisted of a colored square displayed on the screen after each tap. The color indicated whether the index finger extension had reached the upper threshold (Fig. 1C, right). Hence, the motor tasks consisted of five conditions in the following order: repeated press at a slow rate, slow tapping without feedback, slow tapping with feedback, fast tapping without feedback, and fast tapping with feedback.
