Increased sensorimotor activity during categorisation of ambiguous emotional expressions

Actions are rarely devoid of emotional content. Thus, a more complete picture of the neural mechanisms underlying mental simulation of observed actions requires more research using emotion information. The present study used electroencephalography (EEG) to investigate mental simulation associated with facial emotion categorisation. Mu rhythm modulation was measured to infer the degree of sensorimotor simulation. Categorising static images of neutral faces as happy or sad was associated with stronger mu suppression than categorising clearly happy or sad faces. Results suggest the sensitivity of the sensorimotor activity to emotional information rather than visual attentional engagement, because further control analyses revealed (1) no effect of emotion type on occipital alpha modulation, and (2) no difference in mu modulation between the conditions of a control task, which required categorising images with the head oriented right, left, or forward as right or left. This finding provides evidence for the role of the sensorimotor activity in a higher form of mental simulation. Consistent with a predictive coding account of action perception, stronger mu suppression during attempted emotion categorisation of neutral faces may involve minimising the mismatch between predicted kinematics of a happy/sad face and the observed stationarity of neutral faces.