By Karl Zimmer
...When humans mimic others’ faces, in other words, we don’t just go through the motions. We also go through the emotions.
Recently Bernhard Haslinger at the Technical University of Munich realized that he could test the facial feedback theory in a new way. He could temporarily paralyze facial muscles and then scan people’s brains as they tried to make faces. To block facial feedback, Haslinger used Dysport, a Botox-like drug available in Europe.
Botox and Dysport are brand names of a toxin made by the spore-forming bacterium Clostridium botulinum. Botulinum docks on the surface of neurons, blocking the release of a transmitter called acetylcholine. In small amounts botulinum can be fatal. In far, far smaller amounts, it can simply paralyze a small patch of muscles for a few weeks. Haslinger has used Dysport in people with movement disorders like dystonia to help reduce unwanted muscle movement. But Botox and Dysport are best known as treatments to mask aging. Injections into the muscles that make frowns can slow the growth of lines around the eyebrows.
For his brain experiment, Haslinger and his colleagues gave 19 women Dysport injections. Two weeks later the scientists scanned their brains as they showed the women a series of angry or sad faces and asked them either to imitate or just to observe the expressions. Haslinger then ran the same experiment on 19 women without Dysport and compared the two sets of scans.
When the women made sad faces, the same brain regions became active in both those with Dysport and those without. But making angry faces triggered different patterns. In the Dysport-free women, a region known as the amygdala—a key brain region for processing emotions—became active. In the women with Dysport, who could not use their frown muscles, the amygdala was quieter. Haslinger also found another change, in the connections between the amygdala and the brain stem, where signals can trigger many of the feelings that go along with emotions: Dysport made that connection weaker.
Of course neuroscience labs are not the only place where people get shots of Dysport or Botox. According to the American Society of Plastic Surgeons, in the United States doctors administer millions of injections of Botox each year, many of them to people’s faces. Haslinger’s research suggests that this is part of a massive, unplanned experiment.
In June 2008 in the Journal of the American Academy of Dermatology, a team of cosmetic surgeons suggested this experiment is making all of us happier. People with Botox may be less vulnerable to the angry emotions of other people because they themselves can’t make angry or unhappy faces as easily. And because people with Botox can’t spread bad feelings to others via their expressions, people without Botox may be happier too. The surgeons grant that this is just speculation for now. Nevertheless, they declare that “we are left with the tantalizing possibility that cosmetic procedures may have beneficial effects that are more than skin deep.”
Maybe. But for all the Botox youthfulness plastic surgeons may want to think about, neuroscience raises a darker possibility. Making faces helps us understand how other people are feeling. By altering our faces we’re tampering with the ancient lines of communication between face and brain that may change our minds in ways we don’t yet understand.