“When you’re smiling”: how facial expressions affect visual recognition of emotions

Introduction: Facial expressions can elicit simulation in onlookers, and can thus trigger the subjective experience of the same emotion. Moreover, facial muscles activity occurs automatically during the perception of an emotional facial expression (Dimberg and Thunberg, 1998) and preventing it may interfere with the accuracy of emotion recognition (Ponari et al. 2012). However, whether posing a facial expression can shift the perception of ambiguous expressions, and the possible neural basis of this phenomenon, have not been studied. In the present fMRI study we evaluated the effect of posing a facial expression on the recognition of ambiguous emotional faces. Methods: Twenty-six healthy female subjects (mean age 24 + 5,15 years) took part in the experiment. An fMRI event-related paradigm was used. The volunteers were asked to pose a facial expression (happy -H; disgusted –D; neutral -N) according to an emoticon shown on the screen, then to watch a real face expressing an emotion, finally to indicate whether the emotion perceived was happiness (h) or disgust (d). As stimuli, six different ambiguous emotional faces were used; they were a blend of happy and disgusted faces, built from pictures from the Ekman series (Ekman and Friesen, 1976). Three neutral faces (Ekman and Friesen, 1976) were used as controls. The Interpersonal Reactivity Index (IRI, Albiero et al. 2006) questionnaire for empathy was also administered. Functional data were acquired using a Philips Achieva system at 3T and a gradient-echo echo-planar sequence from 30 axial contiguous slices (TR=2000 ms; 326 volumes x 4 sessions; in-plane matrix= 64x64; voxel size: 3x3x4). fMRI analysis was performed using SPM12 (Wellcome Department of Imaging Neuroscience, London, UK). A double statistical threshold (single-voxel statistics and spatial extent) was used to achieve a combined (i.e., corrected for multiple comparisons) significance level of α < 0.05 (3dClustSim AFNI routine). Results: Behavioural results: Posing a disgusted face increased the percentages of d responses (X2=675,2; p< 0.001; Fig. 1a); whereas posing a happy face increased the h responses (X2=119,3; p< 0.001; Fig. 1a) Functional results: Posing happiness and perceiving disgust with respect to posing happiness and perceiving happiness (Hd vs Hh) activated a widespread functional network comprising several left regions (frontal operculum, insula, SMA, medial frontal gyrus, ACC, and basal ganglia, angular gyrus) as well as the right inferior frontal cortex (Figure 1b top). These areas are known to be involved in the a-modal processing of emotions. Posing a neutral face and perceiving happiness with respect to posing a neutral face and perceiving disgust (Nh vs Nd) activated the right posterior insula (Figure 1b bottom). Finally, in several contrasts we found some clusters of increased activity correlating with scores of some subscales of the IRI questionnaire: in particular, high scores in Empathic Concern correlated with the activity of the precuneus in the Ff vs Fd contrast; Fantasy scores correlated with the activity of the right anterior insula within the Df vs Ff contrast and with posterior cingulate and precuneus in the Dd vs Ff contrast. Conclusions: Perceiving a positive, happy face activated the posterior insula, an area consistently activated by pleasurable touch (Morrison, 2016). Behaviourally, posing an emotion shifts the visual perception of ambiguous expressions towards that same emotion. This effect is modulated by the neural system comprising medial and lateral regions of the prefrontal cortex. We can speculate that a cognitive top-down process from the prefrontal cortex could prevent the sensory-motor simulation elicited by the facial expression in being effective on the recognition of others' facial emotions. References Albiero, P. et al. (2006), Contributo all’adattamento italiano dell’Interpersonal Reactivity Index. Test. PSICOMETRIA Metodol. 13, 107–125. Dimberg U and Thunberg M. (1998), Rapid facial reactions to emotional facial expressions. Scand J Psychol. 1998 Mar;39(1):39-45. Ekman, P. and Friesen, W.V. (1976), Pictures of Facial Affect. Consulting Psychologists Press, Palo Alto, CA. Morrison, I. (2016) ALE meta-analysis reveals dissociable networks for affective and discriminative aspects of touch. Hum. Brain Mapp. 37, 1308–1320. Ponari, M et al. (2012), Mapping Correspondence Between Facial Mimicry and Emotion Recognition in Healthy Subjects. Emotion Vol 12(6), Dec 2012, 1398-1403. Schirmer, A and Adolphs, R (2017), Emotion Perception from Face, Voice, and Touch: Comparisons and Convergence. Trends Cogn Sci. 2017 Mar;21(3):216-228. Söderkvist S. et al. (2018), How the Experience of Emotion is Modulated by Facial Feedback. J Nonverbal Behav. 42(1):129-151