Novel popout in vision

A visual analog of mismatch negativity when stimuli differ in duration

Event-linked brain potentials were studied in ten essentially healthy volunteers (six men, four women) aged 18-24 years. Subjects were presented with rare deviant and frequent standard visual stimuli in the standard odd-ball paradigm in conditions of active attention to stimulation and in conditions of distracted attention. Differences between deviant stimuli (50, 100, and 150 msec) and standard (200 msec) stimuli ranged from 50 to 150 msec. Negative difference waves (deviant stimulus with distracted attention minus control stimulus of the same duration) were seen at differences of 100 and 150 msec and these were most marked in the right temporal cortex 200-400 msec from stimulus onset. As this wave was seen in conditions of distracted attention, it appears to be a visual analog of mismatch negativity and reflects the process of the automatic detection of stimuli with deviant durations.

MMN in the visual modality: a review

The mismatch negativity (MMN) component is an event-related potential (ERP) that can be elicited by any change in the acoustic environment, and it is related to memory-based, automatic processing mechanisms, and attentional capture processes. This component is well defined in the auditory modality. However, there is still a great controversy about its existence in the visual modality. This paper reviews the studies that are relevant with regard to memory-based, automatic deviance detection ERPs in the visual system. The paper discusses the main strengths and limitations of those studies and suggests what directions should be taken for future research.

Right hemisphere dominance of different mismatch negativities

Auditory stimulus blocks were presented to 10 reading subjects. Each block consisted of 2 types of stimulus, standard (P = 90%) and deviant (P = 10%), delivered in a random order with short constant inter-stimulus intervals. The standard stimuli were 600 Hz. 80 dB SPL 50 msec sine wave bursts. In different blocks, the deviant stimuli differed from the standards either in frequency (650 Hz), intensity (70 dB) or duration (20 msec). Left- and right-ear stimulations were used in separate blocks. Event-related brain potentials (ERPs) were recorded with 16 electrodes over both hemispheres. All the different types of deviant stimuli elicited an ERP component called the mismatch negativity (MMN). The MMN was larger over the right hemisphere irrespective of the ear stimulated whereas the N1 component, elicited by both standards and deviants, was larger over the hemisphere contralateral to the ear stimulated. The results provide further evidence for the view that the MMN reflects a neural mismatch process with a memory trace which automatically codes the physical features of the repetitive stimuli.