Figure 1.

a, On each trial of the action reprogramming task participants were presented with a centrally displayed white square. Subsequently, two colored flankers (red and green, sides random) appeared on either side of fixation. Four hundred and fifty to six hundred milliseconds after flanker onset, a central colored cue appeared, to which participants responded with the index finger of the hand on the side with the congruent color. Trials were blocked into groups with the same cue color, so that as soon as flankers were presented, participants could anticipate and thus prepare an action based on the cue color presented in the previous trial. The prepared response would, however, be incorrect when the central cue color changed from one trial to the next (switch trials, boxed letters). Correct actions are indicated by “R” (right) and “L” (left). b, The M1 test pulse was applied 75, 125, or 175 ms after the central color cue onset. A pre-SMA conditioning pulse preceded the M1 test pulse by 6 ms on half of the TMS trials.