P300 hemispheric amplitude asymmetries from a visual oddball task.

The P3(00) event-related potential (ERP) was elicited in 80 normal, right-handed male subjects using a simple visual discrimination task, with electroencephalographic (EEG) activity recorded at 19 electrodes. P3 amplitude was larger over the right than over the left hemisphere electrode sites primarily at anteromedial locations (F3/4, C3/4) for target, novel, and standard stimuli. The N1, P2, and N2 components also demonstrated hemispheric asymmetries. The strongest P3 hemispheric asymmetries for all stimuli were observed at anterior locations, suggesting a frontal right hemisphere localization for initial stimulus processing, although target stimuli produced larger P3 amplitudes at parietal locations that did novel stimuli. The relationships of hemispheric asymmetries to anatomical variables, background EEG activity, and neurocognitive factors are discussed.