Automatic Change Detection in Interwoven Sequences: A Visual Mismatch Negativity Study.

In this study, we investigated whether the cognitive system, known to be able to register regular visual event sequences and the violation of these sequences automatically, had the capacity of processing two sequences simultaneously. To this end, we measured the visual mismatch negativity (vMMN) component of ERPs as interwoven event sequences simultaneously presented to the left and right side of the screen. One of the sequences consisted of geometric patterns (diamonds); the other, photographs of human faces. In successive cycles, parts of the stimuli vanished and then re-appeared (the OFF/ON method). The vanishing parts served as either standard (frequently vanishing parts) or infrequent (deviant) events, but these events were task-irrelevant. The 20 adult participants (age 21.40 ± 2.72 years) performed a visual tracking task, with the OFF/ON task being a passive oddball paradigm. According to the results, both OFF and ON events, and both diamond and face stimuli elicited the vMMN component, showing that the system underlying this activity is capable of processing two event sequences if the sequences consist of fairly different kind of objects as stimuli. The sLORETA analysis showed that the source of vMMN was more frequent contralaterally to the deviant event, and the sources comprised loci from ventral and dorsal structures, as well as some anterior loci.

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 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 side and 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) was 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 standardized low resolution brain electromagnetic tomography (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.

Automatic change detection: Mismatch negativity and the now-classic Rensink, O'Reagan, and Clark (1997) stimuli.

Change blindness experiments had demonstrated that detection of significant changes in natural images is extremely difficult when brief blank fields are placed between alternating displays of an original and a modified scene. On the other hand, research on the visual mismatch negativity (vMMN) component of the event-related potentials (ERPs) identified sensitivity to events (deviants) different from the regularity of stimulus sequences (standards), even if the deviant and standard events are non-attended. The present study sought to investigate the apparent controversy between the experience under the change blindness paradigm and the ERP results. To this end, the stimulus of Rensink, O'Reagen, and Clark (1997) was adapted to a passive oddball ERP paradigm to investigate the underlying processing differences between the standard (original) and deviant (altered) stimuli measured in 22 subjects. Posterior negativity within the 280-330 ms latency range emerged as the difference between ERPs elicited by standard and deviant stimuli, identified as visual mismatch negativity (vMMN). These results raise the possibility that change blindness is not based on the lack of detailed visual representations or the deficiency of comparing two representations. However, effective discrimination of the two scene versions requires considerable frequency differences between them.