Visual Search P300 Source Analysis Based On ERP-fMRI Integration

Attention control can be achieved in two ways, stimulus-driven bottom-up attention and goal-driven top-down attention. Different visual search tasks involve different attention control. The pop-out task requires more bottom-up attention, whereas the search task involves more top-down attention. P300 which is the positive potential generated by the brain in the latency of 300-600 ms after the stimulus, reflects the processing of cognitive process and is an important component in visual attention. The P300 source is not consistent in the previous researches, our aim therefore, is to study the source location of P300 component based on visual search attention process. Here we use pop-out and search paradigm to get the ERP data of 13 subjects and the fMRI data of 25 subjects, and analyze the source location of P300 using the ERP-fMRI integration technology with high temporal resolution and high spatial resolution. The target differs from the distractor in color and orientation in the pop-out task, whereas the target and the distractor have different orientation and the same color in the search task. ERP results indicate that pop-out induces larger P300 concentrated in the parietal lobe, whereas search induced P300 is more distributed in the frontal lobe. Further ERP and fMRI integration analyses reveal that the left angular gyrus, right postcentral gyrus of parietal lobe and the left superior frontal gyrus (medial orbital) are the source of P300. Our study suggests the contribution of the frontal and parietal lobes to the P300 component.