Visual mismatch negativity in the "optimal" multi-feature paradigm.

To assess visual mismatch negativity (vMMN) elicited by several deviants in the optimal visual oddball paradigm with a short time, we developed a novel multi-feature vMMN paradigm with five types of deviants integrated in a complex visual context of no more than 20 min. From time to time, the cross in the center of screen throughout the stimulus blocks became bigger or smaller unpredictably. Participants were instructed to ignore the peripheral standard and deviant stimuli on the left and right of the cross and press the left or the right button as quickly and accurately as possible when the size of the cross was changed. Five types of deviant visual stimuli were presented with the solid red rectangles as standard stimuli. Compared to the standard stimuli, each deviant stimulus elicited clearly negative deflection between 150-300 ms post stimulus, with larger amplitudes for orientation vMMN and smaller for size and duration vMMNs. The vMMNs were mainly implemented by the frontal lobe as well as the other cortex areas relevant to different visual features. This time-saving objective measure of vMMNs can be putatively used for studying visual discrimination ability in clinical patients unable to tolerate long-time-span tests.