The visual mismatch negativity is sensitive to

We investigated the sensitivity of visual mismatch negativity (vMMN) to an abstract and nonsemantic category, the vertical mirror symmetry. Event-related potentials were recorded to random and symmetric square patterns, delivered in passive oddball paradigm (participants played a video game). In one of the conditions, symmetric patterns were frequent (standard) stimuli and the random patterns were infrequent (deviant) stimuli, in the other condition the probabilities were reversed. We compared the ERPs to symmetric stimuli as deviants and as standards, and similarly, the ERPs to the random deviants and random standards. As the difference between the ERPs to random deviant and random standard stimuli a posterior negativity emerged in two latency ranges (112–120-ms and 284– 292-ms). These negativities were considered as visual mismatch negativity (vMMN) components. We suggest the two vMMN components are organized in cascade error signals. However, there was no significant difference between the ERPs to the symmetric deviants and symmetric standards. Emergence of vMMN to the deviant random stimuli is considered as a deviation of a perceptual category (in the symmetric standard’s sequence presented). Accordingly, random stimuli acquired no perceptual category, for this reason the symmetric deviant (in the random standard’s sequence presented) elicited no vMMN. The results show that the memory system underlying visual mismatch negativity is capable of coding perceptual categories such as bilateral symmetry, even if the stimulus patterns are unrelated to the ongoing behavior.