Figure 1.

Schematic sequence of events in a trial of the instructed-delay task. The subjects held the joystick-controlled cursor in the center of the display for 3 s. Then, N = 1, 2, or 3 cues (circles) were presented on the screen for 1–1.5 s. The cues indicated the locations at which the upcoming target could appear. The figure shows a case with two cues located at 45° and at 165°. Each cue had the same chance to become the target. In the example, the cue at 45° became the target (disc) onto which the subjects had to move the cursor quickly and accurately. The subjects were instructed to fixate the center of the screen during the trial. The RT was defined as the duration between the onset of the target and the onset of the response, which was determined by the exit of the cursor from the center window. The MT was the duration between the onset of the response and the time when the cursor entered the target. An ITI of 3 s followed each trial.