Facial EMG responses to combat-related visual stimuli in veterans with and without posttraumatic stress disorder

Veterans with (n = 10) and without (n = 10) posttraumatic stress disorder (PTSD) participated in an exploratory study of facial reactivity to neutral slides and to slides depicting unpleasant combat-related material that were previously determined to be emotionally evocative. It was found that the zygomaticus major (cheek), masseter (jaw), and lateral frontalis (forehead) muscles were especially reactive to the combat slides in the veterans with PTSD, suggesting the importance of facial emotional expression in this disorder. The PTSD participants' self-reports of overall distress paralleled these effects. However, autonomic reactivity did not reflect general arousal effects due to the visual stimuli, showing both the sensitivity of facial muscle assessment in this context and the need for further research on the relationship between stimulus modality and physiological trauma reactions. Additional directions for research in this area are discussed including efforts to correlate subjective and physiological reactions.