The brain anatomical basis of emotional face advantage

Abstract

Human beings are quite efficient in emotional face processing, which is of great importance for individuals in their social interactions. Previous studies showed that processing of emotional face was significantly faster than that of neutral face, and individuals showed variability in emotional face processing efficiency. Evidences from functional magnetic resonance imaging researches indicated that brain regions such as amygdala were significantly activated at the present of emotional faces. However, the brain structural basis of this superiority of emotional face processing had not been revealed. The present study combined visual search paradigm and structural magnetic resonance imaging to explore the brain structural basis of individual difference of emotional processing efficiency. In the visual search experiment, we asked the subjects to search for an emotional (a happy or fearful face) face or a target gender (a neutral face). Two-way (set size×target type) repeated measure analysis of RTs were done respective to happy and fearful face and their corresponding face gender search. We found significant interaction of set size and target type for both of them, and the main effects of set size and target type were significant as well. For further analysis, we compare the search slopes of emotional face and face gender search, and found that every subject showed a shallower search function for emotional face search than face gender search, indicating a stable emotional face advantage. Happy and fearful face advantage indexes were calculated for each subject. We then collected structural MRI images of each subject. Then we used multiple regression analysis to explore the correlation between the emotional face advantage indexes and the brain gray matter volume. We found that both the processing advantages of happy and fearful face were significantly correlated with gray matter volume of brain regions in the right posterior cingulate cortex and the left superior parietal lobe. The GMV in the left superior parietal lobe was positively correlated with the emotional face advantage indexes while the GMV in the right posterior cingulate cortex was negatively correlated with them. Previous studies found that superior parietal lobe was involved in attentional shift for different targets, larger GMV of this region might indicate better ability to search a certain target. Posterior cingulate cortex was widely found to participate in the interaction of emotion regulation and memory arousal. It was also an important part in the target-negative network and showed decreased activation in attention-related task, which was consistent with the results in the present study. In addition to these common areas, there were brain areas that only showed correlation with one of the emotional face advantage index. In the fearful face advantage analysis, left temporal gyrus and left posterior cingulate cortex were also significantly correlated with fearful face advantage index. In the happy face advantage analysis, right superior parietal lobe was found to be significantly correlated with happy face advantage index. These results indicated that different emotional face processing included different composition. These results showed that regardless of different composition of different emotional face processing, individual difference for different emotional face processing might have a common brain structural basis.