The effect of unilateral amygdala removals on detecting fear from briefly presented backward-masked faces.

Facial expressions convey information about the moods and intentions of other people and provide important clues about environmental threats. Previous research has shown that patients with unilateral amygdala removals have difficulties rating the intensity of fearful facial expressions. The aim of the current study was to investigate whether patients with amygdala lesions would also be impaired at detecting fear from briefly presented, backward-masked faces. We found that patients with either left or right temporal lobe excisions were impaired at rating fear intensity in faces, whereas fear detection difficulties were predominantly seen in those who had undergone a left temporal lobectomy. Intriguingly, patients with amygdala damage found it more difficult to recognize fear from faces shown for unlimited durations than to detect fear from briefly presented faces. Moreover, there was little overlap between impairments of fear detection and fear-rating, indicating that task demands are crucially important in determining fear-processing deficits.