EVENT-RELATED POTENTIALS TO IRRELEVANT DEVIANT MOTION OF VISUAL SHAPES

Event-related potentials to visual shapes moving across the visual field were recorded from 10 subjects. The subjects had to respond to the appearance of one of the shapes, while other shapes were irrelevant. On the periphery some of the shapes changed their orientation or their form. Sometimes the direction of movement was different from the standard direction. Subjects did not detect the changes of the pattern on the visual periphery, and the ERPs to these non-detected deviants were identical to the ERPs to the standard stimuli. Six subjects detected the irrelevant direction of movement. In these subjects the deviant direction of motion elicited a fronto-central positive wave (P3s) with 322 ms mean latency. There was no such sharp positive peak in the four subjects who did not detect the deviant direction of movement. Unlike the non-target stimuli. the targets elicited a large positive wave (P3b) with 530 ms mean latency.