A couple of days back I posted a link to Ed Yong’s synopsis of the paper just released by Nature purporting to show that modulating serotonin levels in mice could have an effect on their sexual orientation. In short, low- or no-serotonin producing mice no longer discriminated sexually between males and females, mounting cagemates of either gender with equal vigor. There’s really no point in re-summarizing the study as Scicurious has provided an excellent recap.
Here’s a serotonin deficient mouse mounting first a male, then a female:
As the paper’s authors themselves noted, one alternative explanation for the findings is that the loss of gender discrimination was a byproduct of a serotonin-regulated increase in sexual behavior rather then a change in sexual preference per se. Although the study showed that no serotonin mice didn’t show increased sexual behavior towards solo females, they mounted close to 90% of the females in that condition, not leaving a lot of room to show an increase.
Furthermore, mice rely on pheromones to determine who is female and who’s not. The depletion of serotonin might have had some effect on the peripheral olfactory system such that the mice couldn’t distinguish the males from the females. The study did include a control condition which showed mice’s olfactory systems were still at least somewhat functional (they could distinguish between sesame oil and air, and could still identify fox urine.) But maybe the difference between physiological levels of pheromone requires a level of sensitivity in the olfactory system that was lost in the serotonin-depleted animals. I’m not convinced that this explanation has been sufficiently ruled out.
Finally, on a more speculative note, serotonin is known to play a large role in regulating forms of social behavior including aggressiveness and social dominance, in a wide range of species from mice to humans. These animals were completely depleted of serotonin which should lead to significant changes in their social behavior. Past research has associated low serotonin with increased aggressiveness in mammals. Could it be that when male mice mount other males, they are doing something other than “getting it on”? (Male mice with normal levels of serotonin sometimes do mount male mice. Why’s that?).
Although the study’s findings are just the kind of topic that the mainstream media loves (anything involving sex), and they’ve responded with salacious headlines in kind, it seems prudent to interpret the results cautiously and await further work.
It’s no secret that Botox injections can sometimes cause their recipients to become decidedly waxen faced. This presents a quandry for some Hollywood actors, who are under pressure to maintain a youthful appearance but still need to be able to convey emotion on their faces. Sadly, many seem to favor a wrinkle-free visage over faithfullness to their craft.
And there may be even more reason to avoid the Botox needle. A growing body of evidence is suggesting that not only does Botox affect our ability to express emotion, it actually diminishes our emotional experiences. This is due to the phenomenon of psychological embodiment, or, the notion that one’s emotional experiences are not a product of the brain alone, but, rather, are modulated by feed back from the body.
A set of recent experiments have specifically examined the role of facial expression in the processing of emotion. One experiment had subjects read sentences describing pleasant or unpleasant situations while either holding a pen in their mouth (forcing them to smile) or in the lips (forcing them to frown). Participants processed sentences faster when the forced facial expression was congruent with the valence of the sentence, e.g. when smiling during pleasant sentence or frowning during unpleasant sentences. (This effect, and the facial expression produced by the manipulation, occured out of the conscious awareness of the participants.) Previous work has shown that reading words that describe emotions activates specific facial muscles: corrugator supercilli for negative words, and zygomaticus for positive words. These are the primary muscles behind frowns and smiles, respectively. In other words, voluntary activation of specific facial muscles led to downstream effects in emotional experience.
In a new study, researchers at University of Wisconsin- Madison wondered if the relationship would hold if those same muscles were involuntarily deactivated.
Participants — recruited through area cosmetic surgery clinics and given $50 credit towards their Botox treatments — were scheduled for two sessions. In session one, participants read sets of happy, angry and sad sentences. After each sentence, they pressed a key on the keyboard to indicate they’d finished reading. After reading all of the sentences, participants were given a Botox injection. Two weeks later, participants came in for their second session, during which they performed the same reading task they’d performed in session one ( with new happy, angry and sad sentences).
Participants took longer to read angry sentences in session two compared to session one. There was no difference for happy or neutral sentences. This result showed that denervating facial muscles impairs the processing of emotional language, and supports the idea of facial movement as a moderating factor in the bi-directional link between language and emotion.
On one hand, this finding might dissuade some people from going for Botox treatment. The idea of losing one’s full emotional capacity seems a bit distasteful, conjuring up visions of emotional zombieism. On the other hand, the impairment is selective for anger. Could this be an unanticipated benefit? It might be nice to have one’s experience of anger compromised, particularly for those prone with excessive anger problems. Might Botox not have a positive effect on one’s mood (that is, above and beyond the effect of knowing one’s forehead is as smooth as a babies rump?) I can just see the ad now: “Botox: It doesn’t just make you look less angry, but makes you feel less angry.” I’m certainly glad Peter Finch didn’t Botox before his classic scene from “Network” (actors: note the anger lines in the forehead).
Go here for the paper, which includes some interesting speculation as to possible neural and psychological mechanisms.