Figure 1.

Behavioral task. Subjects were instructed to attend the item indicated by the central cue. During set size 1 trials, either the left or right side of the cue was shaded green, indicating that subjects were to attend only the left or right grating, respectively; during set size 2 trials, both sides of the cue were shaded. Subjects were instructed to detect angular deviations in an attended item and to indicate its direction (counterclockwise or clockwise). Stimuli oscillated (3 Hz) for 5 s, followed by a randomly jittered intertrial interval.