The Effects of Valence and Arousal on Hemispheric Asymmetry of Emotion Evidence From Event-Related Potentials

The independent influence of valence and arousal on emotional hemispheric brain asymmetry was investigated to decide between three contrasting hypotheses: the right hemisphere hypothesis, the valence hypothesis, and the integrative hypothesis. Event-related potentials (ERPs) were recorded while participants (N = 20) viewed positive high arousal, positive low arousal, negative high arousal, and negative low arousal pictures, following a baseline measure of ERPs while viewing gray squares. Self-ratings of emotional state in terms of valence and arousal were taken after each of the four emotion blocks. Valence and arousal effects on hemispheric asymmetry were analyzed for the time windows 130-170, 170-280, 280-450, and 450-600 ms. Right dominance on N2 during negative high arousal and left dominance on P3 and late positive potentials during negative low arousal were found over the frontal lobe. Right dominance on P2, P3, and late positive potentials over the parietal lobes appeared during high arousal. No frontal asymmetry was found in positive emotion. Our result partly supported the integrative hypothesis and did not provide evidence for the right hemisphere hypothesis or the valence hypothesis. These results suggested that arousal plays the main role in the ERPs' hemispheric asymmetry.