Encoding of emotional facial expressions in direct and incidental tasks : two event-related potential studies

Emotional face encoding process was explored through electroencephalographic measures (event-related potentials [ERPs]). Previous studies have demonstrated an emotion-specific cognitive process in face comprehension. However, the effect of emotional significance of the stimuli (type of emotion) and task (direct or indirect task) on the ERP is uncertain. In Experiment 1 (indirect task) ERP correlates of 21 subjects were recorded when they viewed emotional (anger, sadness and happiness) or neutral facial stimuli. An emotion-specific cortical variation was found, a negative deflection at approximately 200 ms after simulus (N2 effect). This effect was sensitive to the emotional valence of faces, because it differentiated high arousal emotions (i.e., anger) from low arousal emotions (i.e., sadness). Moreover, a specific cortical site (posterior) was activated by emotional faces but not by neutral faces. In Experiment 2 (direct task), the authors investigated whether encoding for emotional faces relies on a single neural system irrespective of the task, or whether it is supported by multiple, task-specific systems. Differences in the cortical distribution (posterior for incidental task; central and posterior for direct task) and lateralisation (right-distribution for the negative emotions in direct task) of N2 on the scalp were observed in the different tasks. This indicates that distinct task-specific cortical responses to emotional focus can be detected with ERP methodology.