Brain potentials in perception: picture complexity and emotional arousal.

Event-related potentials (ERPs) were measured while participants viewed affectively arousing and neutral pictures depicting either simple figure-ground compositions or more complex scenes to assess the timing and topography of perceptual and emotional modulation. Emotional pictures elicited a larger late positive potential than neutral pictures in a 400-700-ms window over centro-parietal sensors both for pictures with simple figure-ground composition and for more complex scenes. Picture composition affected ERPs beginning earlier (around 150 ms), with simple figure-ground compositions eliciting less positivity over posterior sensors and less negativity over frontal sensors. Emotionality had little effect on modulation of these early ERPs. These data suggest that the late centro-parietal positive potential primarily reflects motivational relevance, and that earlier posterior (and anterior) components reflect, at least in part, differences in a picture's perceptual organization.