Response inhibition in the stop-signal paradigm

Abstract

Response inhibition is a hallmark of executive control. The concept refers to the suppression of actions that are no longer required or that are inappropriate, which supports flexible and goal-directed behavior in ever-changing environments. The stop-signal paradigm is most suitable for the study of response inhibition in a laboratory setting. The paradigm has become increasingly popular in cognitive psychology, cognitive neuroscience and psychopathology. We review recent findings in the stop-signal literature with the specific aim of demonstrating how each of these different fields contributes to a better understanding of the processes involved in inhibiting a response and monitoring stopping performance, and more generally, discovering how behavior is controlled.

Figure 1

Depiction of a trial course in the stop-signal paradigm. Tasks and task parameters in this figure are adapted from STOP-IT, which is a free-to-use stop-signal task program [74]. In the go task, subjects respond to the shape of a stimulus (a ‘square’ requires a left response and a ‘circle’ requires a right response). On one fourth of the trials, the go stimulus is followed by an auditory stop signal after a variable stop-signal delay (SSD). Subjects are instructed to respond as quickly and accurately as possible to the go stimulus on no-stop-signal trials. They are instructed to try to withhold their response on stop-signal trials, but not to wait for the stop signal to occur. On both no-stop-signal trials and stop-signal trials, the stimulus remains on the screen until subjects respond or until the maximal RT has elapsed.

Figure I (Box 1)

(A) Neural activity of FEF movement neurons on no-stop-signal trials and signal-inhibit trials [55]. (B) Neural activity in SEF neurons on no-stop-signal trials and signal-inhibit trials [Data provided by J.D. Schall]

Figure II (Box 2)

(A) Graphic representation of the assumptions of the independent race model [3], indicating how the probability of responding [p(respond|signal)] and the probability of inhibiting [p(inhibit|signal)] depend on stop-signal delay (SSD) (B), the distribution of go reaction times (C), and stop-signal reaction time (SSRT) (D). P(respond|signal) is represented by the area under the curve to the left of each red vertical line.

Figure III (Box 2)

Graphic representation of the assumptions of the interactive race model [64], indicating how go activation on a signal-inhibit trial is inhibited when the stop unit is activated.