The neural basis special for processing fearful expression

Abstract

Objective: To find out the profile of perception of emotion in patients with lesions in bilateral cingulate gyrus, bilateral hippocampus and prefrontal cortex, and to test which of these areas are involved in the special network of fear processing. Methods: A six-basic-emotion continum with 30 morphed emotional faces across happiness-surprise-fear-sadness-disgust-anger-happiness was developed. A labeling task with these morphed emotional faces was administered to measure the ability of recognizing the emotional expressions. Results: A group of 12 cases with prefrontal lesions, showed a gross impairment of recognition of expressions across all 6 basic emotions (the correct scores for 6 basic emotions are 18.41, 16.58, 11.08, 15.67, 12.92 and 15.33 respectively, P < 0.01). Case 1 (with lesion in bilateral hippocampus) showed normal ability in recognizing all emotional faces, but an obvious impairment of episodic memory. Case 2 (with bilateral anterior cingulate gyrus lesions and a very small lesion in the right amygdale) manifested a robust deficit in recognition of fearful expressions (the correct score for fear is 4.67, P < 0.01 in comparison with normal and schizophrenic controls) sparing other emotions except disgust processing (barely borderline different from normal controls). Many cases had shown that unilateral lesion in the amygdala, whether left or right, was not enough to impair fear processing. Although case 2 had a very small lesion in the right amygdala, the result of his performance suggested that bilateral cingulate gyrus, like bilateral amygdala, were selectively involved in fear processing. Conclusions: It is suggested that bilateral amygdala and cingulate gyrus be all selectively involved in fear processing (in parallel or at different levels), while the prefrontal cortex functions as unselective processor for processing of all emotions. It is also possible that hippocampus be involved in the episodic memory, but not in emotional process.