Fig. 1.

Paradigm. (A) In Stop-relevant blocks, a choice-reaction stimulus (a green German traffic-light symbol oriented to the left or right – here represented in light grey – requiring an index / ring-finger response respectively) was either presented for 800 ms (Go-trial) or rapidly replaced by a red Stop-stimulus (here represented in dark grey; Stop-trial). This Stop-stimulus was presented after a variable SOA set by a tracking algorithm and indicated that the response to the Go-stimulus on that trial was to be inhibited, thereby yielding successful (SST) and unsuccessful Stop-trials (UST). (B) In Stop-irrelevant blocks the visual stimulation was identical, but the Stop-stimuli were irrelevant and behavioral responses were required on all trials, thus providing a sensory baseline condition and a reference for response speed in the absence of task-relevant Stop-stimuli.