Affective picture perception: emotion, context, and the late positive potential.

Event-related potentials (ERP) were measured when pleasant, neutral or unpleasant pictures were presented in the context of similarly valenced stimuli, and compared to ERPs elicited when the same pictures were viewed in an intermixed context. An early ERP component (150-300 ms) measured over occipital and fronto-central sensors was specific to viewing pleasant pictures and was not affected by presentation context. Replicating previous studies, emotional pictures prompted a larger late positive potential (LPP, 400-700 ms) and a larger positive slow wave (1-6 s) over centro-parietal sensors that also did not differ by presentation context. On the other hand, ERPs elicited when viewing neutral pictures varied as a function of context, eliciting somewhat larger LPPs when presented in blocks, and prompting smaller slow waves over occipital sensors. Taken together, the data indicate that emotional pictures prompt increased attention and orienting that is unaffected by its context of presentation, whereas neutral pictures are more vulnerable to context manipulations.