ABSTRACT
In this paper, time courses of discrete cortical current sources evoked by target and distractor stimulus are presented in a visual three-stimulus oddball paradigm. 64-channel electroencephalogram (EEG) signals were recorded in healthy subjects in the paradigm where the P3b component of the P300 is evoked in the detection of rare events (target and distractor) and the P3a component is mainly produced by distractor events. A regional source model with constraints of spatial coordinates from fMRI was then applied to event-related potentials (ERPs) data in the target and distractor conditions. Activities of regional sources indicated bilateral inferior parietal lobe, posterior parietal cortex and inferior temporal cortex mainly contribute to the P3b, while the P3a was mainly produced by bilateral insula, bilateral precentral sulcus and cingulate gyrus. Target processing involved parietal lobe, inferior temporal cortex and left insula engaged in stimulus-driven attention process, goal-directed attention process, categorization of visual stimuli and memory retrieval, while distractor processing involved right insula and cingulate gyrus engaged in attention switching and reengagement of attention resource.