FIGURE 1.

Experimental paradigm. (A) Roving visual oddball paradigm with dot motion at five possible directions and two possible coherence levels (low: 5% and high 50%). We manipulated motion coherence: high and low, and motion direction: standard (‘std,’ frequent: no change) and deviant (‘dev,’ rare/surprising: change of direction). The ‘roving design’ meant each deviant motion direction became the new standard direction over repetitions. We presented the task-irrelevant random-dot motion (500 ms per trial) in the visual periphery. Every 5 to 8 ‘standard’ trials the global direction of the dots changed (the ‘deviant’; randomly selected direction). Every 26 to 30 trials (i.e., 13–15 s), we changed both the direction and coherence level of the motion (but discarded EEG events and behavioral responses to these ‘double deviants’). Participants focused on a central 1-back letter task (150 ms ON and 300 ms OFF: desynchronized with most of the motion trials, aligning once every nine trials), responding when the same letter was repeated in succession (e.g., bold letter, ‘B’). Participants were instructed to ignore the motion stimuli and to be as fast and as accurate in the central task. (B) Schematic illustration of the timecourse for motion trials (every 500 ms) and 1-back letter presentation (black rectangles represent 150 ms letter ON).