Figure 1.

Illustration of an SCT. Monkeys were required to push a button (r, gray line) each time stimuli with a constant interstimulus interval duration (s, black line) were presented, which resulted in a stimulus-movement cycle. After four consecutive synchronized movements, the stimuli stopped and the monkeys continued tapping with a similar interval duration for three additional intervals. Hence, six intertap intervals were generated by the monkeys in each trial. The instructed durations, defined by brief auditory or visual stimuli, were 450, 550, 650, 850, and 1000 ms, and were chosen pseudorandomly within a repetition.