Pharmacologic denervation of frown muscles enhances baseline expression of happiness and decreases baseline expression of anger, sadness, and fear.
BACKGROUND
Individuals with intense frowning are commonly perceived as expressing negative emotions. Anger, fear, and sadness are associated with corrugator ("frown") muscle activity.


OBJECTIVE
We sought to study how faces were perceived by others after denervation of frown muscles with localized botulinum toxin injections for treatment of facial frown lines.


METHODS
Facial photographs were taken from volunteers before and after botulinum toxin injection. These photographs were shown to viewers who were naive to the procedure and asked to rate the expressed intensity of anger, sadness, fear, and happiness. As reference for this task we used a standard set of pictures of facial affect displaying different intensity levels for each emotion tested.


RESULTS
Of 40 viewers, 39 were able to discriminate different intensity levels (0%, 25%, 50%, 75%, and 100%) of emotional affect in the control task. According to their ratings faces with denervated frown muscle activity expressed relatively less anger (-40%), fear (-49%), sadness (-10%), and more happiness (+71%).


CONCLUSIONS
Frown muscle activity is essential for both negative and positive emotional expressions. Temporary denervation using botulinum toxin enhances the facial expression of positive emotion resulting in a shift rather than a loss of facial affect.
Heckmann
Marc
M
Department of Dermatology, Ludwig Maximilians Universität, Munich, Germany.
Teichmann
Bianca
B
Schröder
Ulrike
U
Sprengelmeyer
Reiner
R
Ceballos-Baumann
Andrés O
AO
D018726:Anti-Dyskinesia Agents / Q000008:administration & dosage*; D001905:Botulinum Toxins / Q000008:administration & dosage*; D004644:Emotions; D005149:Facial Expression; D005152:Facial Muscles / Q000187:drug effects; D005260:Female; D006801:Humans; D008297:Male; D009121:Muscle Denervation / Q000379:methods; D015588:Observer Variation; D015203:Reproducibility of Results
D018726:Anti-Dyskinesia Agents; D001905:Botulinum Toxins