Human brain potentials related to the emotional expression, repetition, and gender of faces

Abstract

Event-related potentials were recorded from 20 healthy male subjects in response to a large number of color slides of unfamiliar faces with happy, sad, or no emotional expression. In an initial task, the subjects rated the emotional valence of the faces with a joystick. In comparison with neutral faces, both happy and sad faces evoked a larger lateral occipito-temporal negativity from 200 to 400 msec post-stimulus onset. Modulation of late positive complex (LPC: 450-600 msec) by emotional expressions was observed at the frontal sites only in this task, when attention to the emotional valence was required. In a second task, the subjects detected repeating faces among nonrepeating, novel faces. Emotionally expressive faces evoked more negative potential than neutral faces occipito-temporally between 270 and 540 msec latency. Although repetition had a large effect in decreasing the N4 and increasing the LPC, it did not interact with emotional expression, supporting previously proposed independence between processing of a face identity and emotional expression. These findings imply that emotional expression affects early perceptual stages as well as later cognitive stages of face processing. Nonrepeated male faces in both tasks evoked a larger late negativity than female faces.