Should I smile or should I frown? An ERP study on the voluntary control of emotion-related facial expressions.

We investigated the motor planning and reprogramming of facial expressions of happiness and anger with a response-priming task. A response signal commanded the production of a validly or invalidly cued facial expression. Electromyogram showed performance costs of inhibiting the falsely prepared expression and reprogramming the correct one in invalid trials. These performance costs were larger in zygomaticus major than corrugator supercilii, indicating better control over the latter. Event-related potentials indicated no emotion specificity in the initial preparation of anger and happiness in the contingent negative variation. During reprogramming, anger came along with greater allocation of processing resources for the inhibition of the preactivated motor plan (N2), and the updating of a new one (P3). These additional processing resources and the faster control over corrugator may reflect the need for being quick and accurate in displaying threat.