Affective valence and P300 when stimulus arousal level is controlled

Visual stimuli from the International Affective Picture System (IAPS) were employed in a modified oddball paradigm to elicit the P300 event-related brain potential (ERP) in young adult females (N = 12). The pictures varied on valence (negative, neutral, positive) ratings but had the same medium arousal level ratings. The images were presented as targets with a standard stimulus composed of red/white triangles designed to mimic the spatial frequency of the pictures. P300 amplitude from negative relative to neutral stimuli was smaller over frontal areas, whereas amplitude from positive relative to neutral stimuli did not differ. P300 amplitude differences among valence categories were consistent across the midline electrodes, and did not change over the parietal area where arousal effects are typically observed. The findings suggest that valence affects P300 frontal amplitude, and arousal level should be controlled when using emotional stimuli to elicit ERPs. Theoretical implications are discussed.