Anxiety Modulates Perception Of Facial Fear In A Pathway-Specific, Lateralized, Manner

Facial expression and eye gaze provide a shared signal about threats. While averted-gaze fear clearly points to the source of threat, direct-gaze fear renders the source of threat ambiguous. Dual processing routes have been proposed to mediate these processes: reflexive processing via magnocellular (M-) pathway and reflective processing via parvocellular (P-) pathway. We investigated how observers trait anxiety modulates Mand P-pathway processing of clear and ambiguous threat cues. We performed fMRI on a large cohort (N=108) widely ranging in trait anxiety while they viewed fearful or neutral faces with averted or directed gaze. We adjusted luminance and color of the stimuli to selectively engage M- or P-pathway processing. We found that higher anxiety facilitated processing of averted-gaze fear projected to M-pathway, but impaired perception of direct-gaze fear projected to P-pathway. Increased right amygdala reactivity was associated with higher anxiety, only for averted-gaze fear presented to M-pathway. Conversely, increased left amygdala reactivity was associated with higher anxiety for P-biased, direct-gaze fear. This lateralization was more pronounced with higher anxiety. Our findings suggest that trait anxiety has differential effects on perception of clear and ambiguous facial threat cues via selective engagement of M and P pathways and lateralization of amygdala reactivity.