Abstract
Combinations of facial expression and gaze direction can signal danger and are thus important for locating nearby threats. The amygdala complex, including the periamygdalar cortex (PAC), is a key node in the threat appraisal network. When presented briefly (300 ms), fMRI studies found a greater amygdala response to fear faces with averted gaze (Hadjikhani et al. 2008, Adams et al. 2012), which are a clear threat cue. When presentation was sustained (1 s) there was a greater amygdala response to fear faces with direct gaze, which are an ambiguous threat cue (Adams et al. 2012). This threat cue sensitivity has been found to be modulated by state anxiety: individuals with high versus low anxiety scores showed a heightened amygdala response to clear versus ambiguous threat cues, respectively (Ewbank et al. 2010). Here we sought to elucidate the neurodynamics of facial threat cue perception, and examine how they are modulated by perceiver anxiety. Participants (N=43) were shown images of fearful or neutral faces with direct and averted gaze for 1 second. Overall, source-localized MEG activity revealed an early (150-220 ms) PAC response to averted-gaze fear vs. neutral faces, and a later (700-1000 ms) rise to averted-gaze neutral faces, which appear ambiguously fearful (Ewbank et al. 2010). High-anxiety individuals showed a stronger early response to clear threat, but not a differential later response to ambiguous threat (averted neutral), whereas low-anxiety individuals had a brief early response to clear threat and a sustained late response to ambiguous threat. We also found greater responses to direct-gaze fear faces (which are an ambiguous threat cue) versus averted-gaze fear faces (clear threat cue) in PAC (~550 ms) and anterior STS (200-1000 ms). These findings suggest an early reflexive response to clear threat cues and late reflective processing of ambiguous cues that is modulated by perceiver anxiety.
Meeting abstract presented at VSS 2016