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

Abstract

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.

Keywords:

• Facial expression
• Amygdala
• Fear
• Temporal lobotomy
• Emotion

Thanks to Max Coltheart for comments on a previous draft of the manuscript, Amanda Miller Amberber for information on the uncus and Alice Cronin-Golomb for information about the FACT™. Romina Palermo is now in the Department of Psychology, The Australian National University, Australian Capital Territory, Australia 0200.

Notes

¹The data from 1 additional control participant were identified as an outlier on the fear-rating task, and another control participant's data were identified as an outlier on the fear detection task. Their data were removed because their exclusion resulted in the control data becoming normally distributed.

²SINGLIMS individual t tests confirmed that none of the left or right TL patients were impaired at understanding the concept of fear.

³Note that the faces used in this study were sourced from the Gur et al. (2002) database, the same database as that used to select faces for the fear detection task.