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Modulation of amygdala activity for emotional faces due to botulinum toxin type A injections that prevent frowning

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• Open access
• Published: 27 February 2023

Modulation of amygdala activity for emotional faces due to botulinum toxin type A injections that prevent frowning

• Shauna Stark, 
• Craig Stark, 
• Brian Wong & 
• Mitchell F. Brin 

Scientific Reports volume 13, Article number: 3333 (2023) Cite this article

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Abstract

According to the facial feedback hypothesis, when we see an angry or happy face, we contract or flex the relevant muscles to recreate the expression to assist in identifying and experiencing the emotion reflected. We investigated the facial feedback hypothesis by using botulinum toxin type A (onabotulinumtoxinA; onabotA) injections to induce temporary paralysis in the glabellar muscles (responsible for frowning) and measured functional brain activity during the processing of emotional faces. Ten females viewed pictures of happy and angry faces during two functional magnetic resonance imaging (fMRI) scan sessions: one prior (Pre) to onabotA and one following (Active) onabotA injections. We found Pre vs. Active onabotA modulation of activity in the amygdala for both happy and angry faces, as well as modulation of activity in the fusiform gyrus for happy faces. Consistent with our predictions, preventing frowning through inhibition of glabellar muscle contraction altered amygdala processing for emotional faces. The modulation of amygdala and fusiform gyrus activity following onabotA may reflect compensatory processes in a neuroanatomical circuit involved in emotional processing that is engaged when facial feedback is impaired. These data contribute to a growing literature suggesting that inhibition of glabellar muscle contraction alters neural activity for emotional processing.

Clinical Trials.gov registration number: NCT03373162.

 

Getting Botox In This Part Of Your Face Could Actually Decrease Your Happiness Parade, Feb. 27, 2025 A recent study in Nature suggests that getting Botox in the forehead might affect how the brain processes emotions. … Shauna Stark, MS, CCRP, the chief of staff and assistant dean of research operations at UCI School of Medicine, is the study's lead author. Stark and her team wanted to explore whether inactivating the glabellar (frown) muscles would impact the processing of emotional faces. The study put what's known as the "facial feedback hypothesis" to the test.