Emotion effects within frontal alpha oscillation in a picture oddball paradigm

•We examined emotion effects of incidental picture processing within frontal alpha band oscillation.•In an oddball paradigm, valence and arousal were varied within target pictures.•Valence and Arousal were not relevant to the task.•Participants were to press a key in response to any of these target pictures, regardless of their emotional connotation.•Valence had an effect on lateralization of frontal alpha band oscillation.•Arousal had an effect on non-lateralized frontal alpha band oscillation.•Both effects were evident, even if we controlled for subjective ratings of valence and arousal.

In the current study we measured frontal alpha band oscillation in an oddball paradigm with emotional pictures as target stimuli. Within these emotional target pictures we varied valence and arousal separately. Irrespective of this emotional connotation, participants were asked to respond to the occurrence of any picture that deviates from the standard picture (a checkerboard). All stimuli were presented briefly and target stimuli were easily distinguishable from the standard stimulus based on mere perceptive features. Thus, the procedure reduces the probability that participants intentionally process or evaluate the emotional content of the pictures. With these incidental procedural conditions we yet observed a relative shift of alpha power to the right frontal site with increasing pleasantness of the pictures. Furthermore, frontal alpha band oscillation decreased with increasing picture arousal. These patterns were also evident when we controlled for valence and arousal of the pictures at the individual level. The results suggest that changes in frontal alpha band oscillation reflect reliable emotion correlates of incidental picture processing in the oddball paradigm.