Emotion unfolded by motion: a role for parietal lobe in decoding dynamic facial expressions

Abstract

Facial expressions convey important emotional and social information and are frequently applied in investigations of human affective processing. Dynamic faces may provide higher ecological validity to examine perceptual and cognitive processing of facial expressions. Higher order processing of emotional faces was addressed by varying the task and virtual face models systematically. Blood oxygenation level-dependent activation was assessed using functional magnetic resonance imaging in 20 healthy volunteers while viewing and evaluating either emotion or gender intensity of dynamic face stimuli. A general linear model analysis revealed that high valence activated a network of motion-responsive areas, indicating that visual motion areas support perceptual coding for the motion-based intensity of facial expressions. The comparison of emotion with gender discrimination task revealed increased activation of inferior parietal lobule, which highlights the involvement of parietal areas in processing of high level features of faces. Dynamic emotional stimuli may help to emphasize functions of the hypothesized 'extended' over the 'core' system for face processing.

Keywords: dynamic facial expressions; emotion perception; emotion–cognition interaction; inferior parietal lobule.

Fig. 1

Angry and happy face stimuli at four morph levels were arranged across expression intensity and gender dimensions. Depicted are the final frames for the 1000 ms video displays.

Fig. 2

Mean results of ratings. X-axis: four intensity levels. Y: mean rating by participants on a scale from 1–4; N = 20.

Fig. 3

(Top) RFX group maps of the two contrasts of interest. (Upper row) main effect of emotion intensity shows an enhancement of BOLD responses in a network of motion-responsive areas, including bilateral hMT+/V5, right V3a and postcentral gyrus. No cluster in the whole-brain analysis showed greater response to less dynamic faces, i.e. low intensity > high intensity (P > 0.1). (Lower row) Main effect of emotion rating vs gender rating shows a bilateral activation of IPL. (Bottom) Beta-values extracted from the second level RFX GLM analysis in sample regions confirm a main effect of emotion rating vs gender rating in the bilateral IPL and an interaction effect of valence × intensity in the right postcentral gyrus. GA, gender task/angry faces; GH, gender task/happy faces; EA, emotion task/angry faces; EH, emotion task/happy faces; A1-4, angry faces/intensity 1-4; H1-4, happy faces/intensity 1-4.