Background and Objective
Major depressive disorder (MDD) is a common condition for which available pharmaceutical treatments are not always effective and can have side-effects. Therefore, alternative and/or complementary MDD treatments are needed. Research on facial expressions has shown that facial movements can induce the corresponding emotions, particularly when specific attention is paid to voluntarily activating muscles that are typically only activated involuntarily while expressing emotions. We hypothesized that functional electrical stimulation (FES) applied to facial muscles may enhance this effect due to its ability to modulate central nervous system plasticity. Thus, applying FES to the facial muscles associated with smiling (including the “Duchenne marker”) may increase the activity of subcortical nuclei related to positive emotions and counteract symptoms of depression.