Authors:

EWBANK, M.P., Nummenmaa, L., CALDER, A.J.

Reference:

Year of publication:

2008

CBU number:

6830

Abstract:

Individual differences in anxiety have been shown to be a critical factor in determining the amygdala response to facial expressions of fear. However, the influence of anxiety and the amygdala’s role in processing other facial signals of threat is less understood. Angry faces also represent a potent signal of danger, however the nature of threat signalled by angry and fearful faces is thought to be qualitatively different. While fearful faces signal the presence of danger within the environment, angry faces signal a more direct and immediate form of threat; (i.e. the aggressor). Consistent with previous research, we have demonstrated that high anxious individuals show an increased amygdala response to fearful faces presented both inside and outside the focus of attention. By contrast, high anxious individuals showed an increased amygdala response to angry faces only when the faces were attended. These results suggest the level of threat or danger signalled by a face is differentially modulated by the focus of attention. Studies investigating the effect of eye gaze on the perception of facial expression also indicate that the intensity of angry facial expressions is enhanced when the face displays a direct (or mutual) gaze. Based upon these findings, our hypothesis was that high anxious individuals would show an increased amygdala response to angry faces only when seen with mutual gaze. By contrast, the response to fearful faces should be less dependent upon gaze direction. To address this, we used event-related fMRI to examine the effects of anxiety and gaze on the neural response to angry and fearful faces. Participants viewed images of fearful, angry and neutral faces, either displaying an averted or mutual gaze. The results revealed a positive correlation between anxiety and the amygdala response to both mutual and averted gaze fearful faces compared to neutral faces. By contrast, we found an increased amygdala response in high anxious individuals only to mutual gaze angry faces relative to neutral faces. These results are consistent with the differing nature of threat signalled by angry and fearful facial expressions, and support the role of the amygdala as part of a warning system involved in the detection of danger. Furthermore, these findings emphasise the importance of individual differences in anxiety when considering the amygdala response to facial signals of threat.