Sci saw this paper come out last week, it made it big in the mainstream media, and a couple of blogs covered it. Whenever something like this comes up in the news, I just have to get the paper myself and make sure whether it's all really true. And now I have it, so here we go.
Wagner, et al. "Spontaneous Action Representation in Smokers when Watching Movie Characters Smoke". The Journal of Neuroscience, 2010.
We'll start with a recollection. Sci spent a lot of her young life (ok ok, also her adult life. And now) as a dancer. Various types, but this memory comes from ballet.
I recall one rehearsal before a performance. Another piece was on stage, the rest of the ballet was watching in the wings and in the audience. There was a whole row of us in the seats, watching. I felt my leg start to jerk. I look down, and realize my leg muscles are moving, because I'm viewing dance and my body wants to DANCE. Then I looked down the row. Up and down the row of dancers, legs were jerking, spontaneous muscle movements from dancers watching dance. To this day, when I see dancing, my legs will jerk, because my body wants to dance, too. Just THINKING about it, my leg started jerking. RIGHT NOW. Yeesh.
This is the physical representation of the action observation network (AON), areas in the brain which are activated in response to meaningful actions. When you see a goal directed action that has meaning to you, these brain regions will activate, and you will begin to plan the action as though you were to do it yourself. If the stimulation is strong enough, you may actually follow through with some of the action, as with the dancers and our jerking legs. In fact, the AON has been shown in dancers themselves.
But what about in smokers? And why would it matter? As we all know, smoking is highly addictive, and highly bad for you. Many studies have gone into what makes it so addictive, and what makes it so easy to get hooked. One of the things that could be involved in the addictive properties of smoking (other than the good old reward related brain areas) is the AON. Craving and relapse could be as simple as just watching someone light a cigarette, as their motions prompt you to do the same.
Now, a lot of studies have already looked at smokers in MRI machines. What was different about this one was the difference between a movie and a photo. Usually, when scientists go to study drugs of abuse and craving in humans, they use photos of drug paraphernalia to study craving, and what brain areas are associated with it. But while photos can help study craving, they can't really help study whether drug use is associated with things like motion (or the AON), because a photo isn't IN motion. So to look at the involvement of the AON, you have to get some photos in motion.
To test this, the authors of this paper grabbed smokers and non-smokers, plunked them in an MRI, and showed them a MOVIE. Sadly, they didn't show them Mad Men (which is pretty well covered in a smoky haze), they showed them the movie Matchstick Men. They then checked to see what areas of the brain lit up in the smoking scenes vs the non-smoking scenes (which served as a control).
What you can see on the top left are the main areas that showed a higher activation in smokers vs non-smokers. The graphs on the bottom show the two most important areas, the intraparietal sulcus (IPS) and the left lateral profrontal cortex (LPFC). Both of these areas showed a large response in smokers during scenes depicting smoking, and both of these areas are part of the AON.
So it appears that, like dancers watching dancing, a smoker watching smoking "goes through the motions" in their brain, planning the motion of lighting up.
All this is very cool, and it's nice to see it "in motion" as it were. The authors also noticed that there was activity in drug cue-related regions like the nucleus accumbens and orbitofrontal cortex. But what I found most interesting was a tiny little paragraph at the end of the results section, where they discussed craving.
The dorsal anterior cingulate cortex mentioned above is an area of the brain that is associated with the motor cortex (as opposed to the ventral anterior cingulate cortex which is associated more with reward related structures). And it was ALSO an area of the brain where activity level during the smoking scenes correlated with cigarette craving after the scan. This is not particularly surprising, and has been noted before in other studies, but this is the first time I have particularly seen it associated with motion and the actions associated with lighting up a smoke. And it means that more of craving than we realize may be linked to the association with certain motor cues that become ingrained, like positioning a cigarette for a light.
The implications for this study are pretty obvious. If you're trying to quit smoking, it's best to stay away from movies or TV shows depicting smoking, which might induce craving and cause you to relapse. But it's harder than you might think. It's not an easy thought to keep in mind (does this movie involve smoking?), and many episodes of smoking in TV shows are very ubiquitous and hard to avoid. And it shows us just how delicate some of the cues can be to make us fall into the trap of relapse.
Wagner DD, Dal Cin S, Sargent JD, Kelley WM, & Heatherton TF (2011). Spontaneous action representation in smokers when watching movie characters smoke. The Journal of neuroscience : the official journal of the Society for Neuroscience, 31 (3), 894-8 PMID: 21248113