Neuromodulation of emotion using functional electrical stimulation applied to facial muscles.
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.


METHODS
Twelve able-bodied subjects received FES and were compared with a group of 12 control subjects. Both groups underwent the same experimental procedures involving a cognitive task, and a deception was used such that subjects were unaware that the objective was to modulate mood. Assessments with the Positive and Negative Affect Schedule-Expanded Form (PANAS-X) were administered before and after the experiment.


RESULTS
No significant between-group differences were found in the change scores for our primary outcomes, the PANAS-X item "happy," and aggregate scores "Joviality" and "Positive Affect." Significant differences were, however, detected for secondary outcomes "determined," "daring," "scared," and "concentrating."


CONCLUSIONS
These results suggest that modulating emotion using FES may be possible, but is difficult to target accurately. Further work is warranted to explore FES applications to MDD.