Event-related potential P2 derived from visual attention to the hemi-space. Source localization with LORETA

This study aimed to measure event-related potential P2 using electroencephalography (EEG), and to locate equivalent current sources related to visual attention in the hemi-space. The amplitude of P2 increases when subjects perceive the stimuli or pay attention to the stimuli. Six volunteer subjects were directed to look at a train of visual oddball stimuli. The oddball stimuli consisted of a square on one side and a circle on the other side of the visual field. Subjects were requested to push a button at the visual cue 800 ms after the target stimuli were displayed. EEG activities were recorded at 64 points over the head. Low-resolution brain electromagnetic tomography (LORETA) was used for the source estimation. Event-related potential P2 was observed at around 200 ms after the onset of the target stimuli. The activity of the parietal and frontal region at P2 changed according to the attention to the hemi-visual field. The activity of the P2 may be located on the parietal lobe, and the frontal lobe (the frontal eye field) may be also activated according to the attention.