Having spent the last three years studying how difficult it is to say no to our vices, and being intimately acquainted with all that can go wrong in fMRI research, I’m always a bit skeptical of studies that claim to be able to predict our capacity for self-control based on a brain scan. But a new paper out this week in Psychological Science seems to have done a pretty admirable job, tying our real-life ability to resist temptation with activity in two specific areas of the brain.
Researchers from Dartmouth University first tested 31 women on two different tasks: an assessment of self-control and a measurement of temptation. Using an fMRI scanner, they compared where the women’s brains lit up when they were stopping themselves from performing a certain action (pressing a button, to be exact), and when they were seeing images of ice cream, hamburgers, and other tasty treats. As expected, better performance on the response inhibition task was linked to activation in a part of the brain called the inferior frontal gyrus (IFG), a region in the frontal cortex known to be involved in inhibiting a response. Conversely, looking at pictures of chocolate and chicken sandwiches activated the nucleus accumbens (NAcc) a deeply rooted part of the brain that’s essential in feelings of reward.
So far, this is all pretty par for the course; you exert self-control, you activate your control center. Looking at something enticing? Your reward region is going to light up. Nothing new or ground-breaking (or even that useful, to be honest). But the researchers didn’t stop there. Instead, they took the study out of the lab to see what happened when the participants were faced with real-life temptations. Equipping them with Blackberry smartphones, the participants were prompted throughout the week with questions about how badly they desired junk food, how much they resisted these cravings, whether they gave in to their urges, and how much they ate if they did cave to temptation.
Comparing these responses to brain activity in the two target areas, the researchers discovered that the women who had the most activity in the NAcc while viewing images of food were also the ones who had the most intense cravings for these treats in real life. Additionally, these women were more likely to give in to their temptations when they had a hankering for some chocolate. On the other hand, those who had greater activity in the IFG during the inhibition task were also more successful at withstanding their desires — in fact, they were over 8 times more likely to resist the urge to indulge than those with less activity in the region. And if they did give in, they didn’t eat as much as those with a smaller IFG response.
Having confirmed the link between activity in these areas and real-life behaviors, the next step is to figure out how to ramp up or tamp down activity in the IFG and NAcc, respectively. One technique that psychologists are exploring is transcranial magnetic stimulation, or TMS. This involves zapping a certain part of the brain with an electromagnetic current, trying to either stimulate or depress activity in that region. So far, use of TMS in studies of addiction and eating disorders — attempting to enhance self-control and decrease feelings of craving — has been met with limited success. Pinpointing the exact right area through the skull and figuring out the correct frequency to use can be difficult, and in fact, a few studies have actually accidentally increased desire for the substance! Additionally, the effects are often temporary, wearing off a few days after the stimulation is over. Other studies have looked at cognitive training to try to enhance self-control abilities, particularly in children with ADHD, although these attempts have also varied in their success.
Beyond targeting certain psychiatric disorders or trying to get us to say no to that second (or third or fourth) cookie for reasons of vanity, there’s a push to enhance self-control from a public health standpoint. The authors of the current study cite the staggering statistic that 40% of deaths in the U.S. are caused by failures in self-control. That’s right, according to research, 40% of all fatalities are caused by us not being able to say no and partaking in some sort of unhealthy behavior, the biggest culprits being smoking and over-eating or inactivity leading to obesity. Clearly then, improving self-control is not only needed to help individuals on the outer edges of the spectrum resist temptation, it would benefit those of us smack dab in the middle as well.
This is is super interesting. Do you know if there are any studies that have been done to try to link to any kind of genetic component to regulation of the NAcc?
I’m not sure about direct genetic links to the NAcc itself, but the other key component in all of this is the neurotransmitter dopamine, for which there are several key genes that have been identified. Both drug addiction and ADHD have been tied to abnormalities in dopamine processing in the NAcc (and prefrontal cortex), which are thought to contribute to the impulsivity, reward sensitivity, and difficulties in self-control that are characteristic of the disorders. Genes affecting dopamine release, receptor availability, and transporter reuptake have all been identified, not to mention other genes that affect the breakdown and metabolism of dopamine and other neurotransmitters.
40% of the deaths in the US are due to failures in self control?
I wonder what percentage of the births (ok, conceptions) can be chalked up to the same.