The role of inhibitory mechanisms in the regulation of facial expressiveness during pain.

Although it is assumed that inhibitory control plays a role in regulating the degree of facial expressiveness, so far the specific type of inhibitory mechanism involved has not been identified. The present study was designed to investigate the association between different types of inhibitory mechanisms and the degree of facial expressiveness. Facial expressiveness during experimental pain was assessed using the Facial Action Coding System and facial electromyography (criterion variables). Different aspects of inhibitory functioning (Antisaccade task, Stroop task, questionnaire) were used as predictor variables. The degree of facial expressiveness was significantly predicted by the performance in the Antisaccade, but not the Stroop task or the questionnaire. The higher the ability was to inhibit saccadic eye movements, the lower was the degree of facial expressiveness. This data suggests that the degree of facial expressiveness is not regulated by inhibitory control in general, but specifically depends on inhibitory mechanisms regulating automatic motor responses.