Figure 1.

Proactive selective inhibition task. The task was designed to study the influence of prior information about inhibition targets on behavior and neural responses. Responses were made using both index or middle fingers, the four circles on the screen corresponding to fingers on a keypad as indicated by the lower left inset. At the start of each trial faded red crosses cued the participant about the potential locations of a stop signal. In the Informed condition this would be either both the left or right circles (left or right hand, respectively), in the Uninformed condition the stop signal could appear over any of the four circles, and in the noStop condition there would never be a stop signal. After a jittered anticipation period a Go cue was presented, comprised of four circles with either the top or bottom two filled. The fingers corresponding to the filled circles had to press down as fast as possible. In the Informed and Uninformed condition a stop signal was presented on 30% of trials after a staircased stop-signal delay. The location of the stop signal always followed the restrictions set by the cue (i.e., the cued side in Informed condition, or either side in Uninformed condition). Participants had to stop the finger corresponding to the stop signal, but still go with the finger corresponding to the filled circle without the stop signal. No feedback was provided.