Automatic detection of irregular vanishing and reappearing parts of objects in two interwoven sequences: A visual mismatch negativity study.

The cognitive system automatically develops predictions on the basis of regularities of event sequences, and reacts to the violation of these predictions. In the visual modality the electrophysiological signature of this process is an event-related potential (ERP) component, the visual mismatch negativity (vMMN). So far, we have no data, whether the system underlying vMMN is capable of dealing with more than one event sequence simultaneously. To disclose this aspect of the capacity of the system, in a passive oddball paradigm, we presented two interwoven sequences. The stimuli were objects (diamond patterns with their diagonals), one of the sequences was presented to the left, the other to the right side of the visual field. From time to time two parallel lines of the diamonds disappeared (OFF event), and then reappeared (ON event). The frequently vanishing pair of lines on the left side (standard) were identical to the rarely vanishing lines of the objects on the right side (deviant), and vice versa. We found that deviant ON events elicited vMMN only for left-side deviants, and deviant OFF events elicited vMMN only for right-side deviants. The sLORETA source localization showed vMMN sources both in posterior visual structures and in anterior locations, and activity was stronger in the hemisphere contralateral to the deviant event. According to the results, the system underlying vMMN is capable of dealing with two sequences, but within a sequence it detected only one type (either OFF or ON) of deviancy.