In visual oddball studies, deviant compared to standard stimuli elicited a posterior negative ERP at around 100-250 ms. To determine the underlying processes of the negativity, we used the equiprobable sequence in which bar stimuli of five types of orientation were presented with equal probabilities (control 20% each) as well as the oddball sequence in which two stimuli with the closest orientation were presented with different probabilities (deviant 20% and standard 80%). Deviant compared to standard stimuli elicited two negativities at around 100-150 ms with no hemispheric dominance and 200-250 ms with right hemispheric dominance, while deviant compared to control stimuli elicited only a negativity at around 200-250 ms with right hemispheric dominance. These results suggest that the early negativity reflects refractory effect, while the late negativity reflects memory-comparison-based change detection effect (visual mismatch negativity).
P300 differences for target (.10), nontarget (.10), and standard tones (.80) were assessed using a three-stimulus oddball paradigm in which participants responded only to the target (n = 12). Target/standard (easy or difficult) and nontarget/standard (large or small) pitch differences were manipulated orthogonally. In all conditions, target tones elicited a parietal P300, which was affected only by the target/standard discrimination ease. Nontarget in the easy/large and difficult/small conditions elicited a parietal but smaller P300 than the target but in the easy/small condition elicited similar ERPs to the standard. However, nontarget stimuli in the difficult/large condition elicited an anterior maximum and earlier P300 (P3a) component. The findings suggest that target P300s are not influenced by the nontarget stimulus configuration, whereas the nontarget P300 outcomes are determined directly by the stimulus context. The theoretical implications are discussed.
P300 differences for target (.10), nontarget (.10), and standard tones (.80) were assessed using a three-stimulus oddball paradigm in which participants responded only to the target (n = 12). Target/standard (easy or difficult) and nontarget/standard (large or small) pitch differences were manipulated orthogonally. In all conditions, target tones elicited a parietal P300, which was affected only by the target/standard discrimination ease. Nontarget in the easy/large and difficult/small conditions elicited a parietal but smaller P300 than the target but in the easy/small condition elicited similar ERPs to the standard. However, nontarget stimuli in the difficult/large condition elicited an anterior maximum and earlier P300 (P3a) component. The findings suggest that target P300s are not influenced by the nontarget stimulus configuration, whereas the nontarget P300 outcomes are determined directly by the stimulus context. The theoretical implications are discussed.
The evaluation of whether an outcome is good or bad is reflected in feedback-related negativity (FRN), which is an event-related brain potential (ERP) component that is elicited by bad events. It is still, however, unclear how the FRN reflects the evaluation of outcomes induced by others. We focused on the relationship between self and other, and recorded ERPs during an alternative gambling task performed by two players (participant and virtual player). FRN was elicited not only by the losses of another in a cooperative situation but also by the gains of another in an antagonistic situation. These results indicate that FRN reflects the evaluation on the basis of one's own evaluative criteria, regardless of the monetary outcome for another.
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.
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