Emotional expression boosts early visual processing of the face: ERP recording and its decomposition by independent component analysis

To investigate the hypothesis that early visual processing of stimuli might be boosted by signals of emotionality, we analyzed event related potentials (ERPs) of twelve right-handed normal subjects. Gray-scale still images of faces with emotional (fearful and happy) or neutral expressions were presented randomly while the subjects performed gender discrimination of the faces. The results demonstrated that the faces with emotion (both fear and happiness) elicited a larger negative peak at about 270 ms (N270) over the posterior temporal areas, covering a broad range of posterior visual areas. The result of independent component analysis (ICA) on the ERP data suggested that this posterior N270 had a synchronized positive activity at the frontal-midline electrode. These findings confirm that the emotional signal boosts early visual processing of the stimuli. This enhanced activity might be implemented by the amygdalar re-entrant projections.