Differential visual pathway contributions to compound facial threat cue processing

Abstract

Facial expression can be a threat cue whose meaning depends on the direction of eye gaze. For example, fear combined with averted eye gaze clearly signals threat and its location, while a direct gaze leaves the location ambiguous (Adams et al., 2012). Processing of clear and ambiguous threat cues is thought to differentially involve the major visual pathways: magnocellular (M) pathway for rapid processing of clear threat and parvocellular (P) pathway for slower processing of threat ambiguity (Adams et al., 2012, Kveraga, 2014). Here we sought to characterize neurodynamics while perceiving threat from faces that were biased towards M or P pathways, or unbiased two-tone images. Participants (N=58) viewed a series of direct and averted gaze fearful and neutral displays, each for 1s. We extracted source-localized MEG activity and computed direction of information flow via phase-slope index (PSI) analysis in select regions of the face-processing network: primary visual cortex (V1), fusiform face area (FFA), periamygdaloid cortex (PAC), posterior superior temporal sulcus (pSTS), and orbitofrontal cortex (OFC). We found that early activity in V1 lead activity in FFA (p=0.001) and in PAC (p=0.007) for P-biased compared to M-biased faces. In fear > neutral faces, activity in left PAC and FFA was modulated by pathway, with PAC leading for M-biased and FFA leading for P-biased fear faces (p=0.03). With increased threat ambiguity, OFC led activity in pSTS later in the trial for both unbiased faces (p=0.005) and for M/P-biased faces (p=0.003), suggesting reflective processing to interpret the meaning of the cue. These results suggest an early role of feedforward processing for parvocellular inputs, evidenced by its flow from V1 and pSTS, and indicate feedback based from magnocellular inputs, as evidenced by its flow from PAC to FFA. Our findings describe the dynamics of information flow for M/P contributions to emotional face perception.

Meeting abstract presented at VSS 2017