No abstract

In ERP studies, two posterior components with different polarities have been identified as ERP correlates of visual change detection. To compare these components in terms of sensitivity to the preceding stimulus sequence, two peripheral stimuli of different colors (red and blue) were presented with equal (50:50) or different probabilities (20:80 or 80:20), while 12 participants performed shape discrimination at a central location. A posterior positivity at around 90–140 ms was observed with similar amplitude to all stimuli immediately preceded by a different stimulus. In contrast, a posterior negativity at around 140–180 ms was observed to increase in amplitude with increasing number of preceding different stimuli. These results suggest the existence of probability‐independent and ‐dependent change processing in the human visual system. The functional significance is discussed in terms of memory‐based comparison and stimulus‐specific refractoriness.

To elucidate the nature of the processing of visual stimulus changes, ERPs were recorded while 12 participants performed an S1-S2 matching task with multifeature stimuli. Each trial consisted of two sequentially presented stimuli (S1-S2), where S2 was either the same as S1, different from S1 only in color, different only in shape, or different in both color and shape. The four trial types were presented in random order with equal probability, and participants responded to one of these types in separate blocks. Relative to the no-change stimuli, the change stimuli elicited posterior positivity with different topography according to changing features ranging from 100 to 180 ms in all tasks. The amplitude and topography of the positivity in response to the both changes were the respective sums of those to changes in the corresponding single features. These results suggest that a feature-specific change detection system exists in the human visual system.

No abstract

The involvement of memory-comparison-based change detection in visual distraction was elucidated. Not only luminance increments that engaged memory-comparison-based change detection and refractoriness-based rareness detection but also luminance decrements that engaged only memory-comparison-based change detection caused behavioral distraction, which was mirrored by a posterior negativity (240-260 ms, posterior N2) and a broad positivity (420-460 ms, P3a) that reflected attentional capture. Preceding these effects, luminance increments elicited a posterior positivity (100-120 ms, change-related positivity) and a posterior negativity (120-140 ms, change-related negativity), whereas luminance decrements elicited only a posterior positivity (160-180 ms, change-related positivity). These results suggest that memory-comparison-based change detection indexed by change-related positivity is involved in visual distraction as a result of attentional capture.