Stimulus context determines whether non-target stimuli are processed as task-relevant or distractor information.
OBJECTIVE
The P300 event-related brain potential (ERP) was elicited using a visual three-stimulus oddball paradigm (standard 0.70, target 0.15, non-target 0.15) to examine how target/standard stimulus context affects non-target processing.


METHODS
Target/standard discrimination difficulty (easy or difficult) and non-target /target similarity (similar or dissimilar) were manipulated orthogonally. Participants (N=13) were instructed to respond to each infrequent target stimulus by pressing a button.


RESULTS
Target stimuli in all task conditions elicited P3b, which was affected only by the difficulty of target/standard discrimination. When target/standard discrimination was easy, the amplitude of non-target P3 was larger for similar than for dissimilar non-target. In contrast, when target/standard discrimination was difficult, non-target stimuli elicited P3a, the amplitude of which was larger for dissimilar than for similar non-target. Thus, the P300 component for non-target stimuli and the pattern of the effect of target similarity on each P300 component varied as a function of the target/standard stimulus context.


CONCLUSIONS
The target/standard stimulus context influences the attentional set for stimulus processing such that it determines whether non-target stimuli are processed as task-relevant or distractor information.


CONCLUSIONS
The present results are important for understanding the mechanism of cognitive modification in non-target processing.
Sawaki
Risa
R
Graduate School of Education, Hokkaido University, Sapporo 060-0811, Japan. sawaki@edu.hokudai.ac.jp
Katayama
Jun'ichi
J
D000328:Adult; D001288:Attention / Q000502:physiology; D001931:Brain Mapping; D003627:Data Interpretation, Statistical; D004192:Discrimination, Psychological / Q000502:physiology; D004569:Electroencephalography; D018913:Event-Related Potentials, P300 / Q000502:physiology*; D005071:Evoked Potentials / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D009949:Orientation / Q000502:physiology; D010775:Photic Stimulation; D011597:Psychomotor Performance / Q000502:physiology; D011930:Reaction Time / Q000502:physiology