Tracing the time course of emotion perception: the impact of stimulus physics and semantics on gesture processing

Numerous event-related brain potential (ERP) studies reveal the differential processing of emotional and neutral stimuli. Yet, it is an ongoing debate to what extent the ERP components found in previous research are sensitive to physical stimulus characteristics or emotional meaning. This study manipulated emotional meaning and stimulus orientation to disentangle the impact of stimulus physics and semantics on emotional stimulus processing. Negative communicative hand gestures of Insult were contrasted with neutral control gestures of Allusion to manipulate emotional meaning. An elementary physical manipulation of visual processing was implemented by presenting these stimuli vertically and horizontally. The results showed dissociable effects of stimulus meaning and orientation on the sequence of ERP components. Effects of orientation were pronounced in the P1 and N170 time frames and attenuated during later stages. Emotional meaning affected the P1, evincing a distinct topography to orientation effects. Although the N170 was not modulated by emotional meaning, the early posterior negativity and late positive potential components replicated previous findings with larger potentials elicited by the Insult gestures. These data suggest that the brain processes different attributes of an emotional picture in parallel and that a coarse semantic appreciation may already occur during relatively early stages of emotion perception.