Thank you for your comments on last week’s Weekly Brain Update.
The July 3 issue of the Journal of Neuroscience was full of interesting articles and has provided yet another example of how the prefrontal cortex relates to knitting. I wonder if this will be the case every week? I did try my best to devise a link with other articles, ones that focused on hyperalgesic priming, enhanced visual cortex activity in people with amygdala damage, epigenetic regulation of novelty-seeking, and monkey eye-hand coordination, but the prefrontal cortex paper won.
In the article entitled Ventromedial Prefrontal Cortex Encodes Emotional Value, the authors frame their work in terms of neuroeconomics*: decision making with regard to money is dependent on brain-mediated emotional experiences, both negative and positive. One example that they give is how a nice garden might induce potential home-buyers to spend more on a house than they would otherwise. There is also evidence that positive emotion increases the likelihood of impulsive spending, a common experience to anyone who never leaves their favorite yarn store empty-handed.
Regulating positive emotion is also important if you’re trying to limit your food intake. The sight of a cake, or a bag of chips, or a stack of chocolate chip cookies automatically stimulates the reward areas of the brain, including the ventromedial prefrontal cortex (vmPFC), which computes the value of those items and makes a comparison with one’s eventual goals, such as fitting into last year’s Fall wardrobe. When making a decision about whether to convert the action of looking to that of eating, research suggests that how enticing the object is perceived and how easy it is to resist relates to one’s ability to regulate emotion. If you are able to redefine the cake as a mixture of oil, sugar, and flour and to talk yourself out of eating it, you have probably done so because you’ve lowered the value of the cake by decreasing the activity in your vmPFC.
Do you find the mere sight of yarn to be a positive emotional experience? After years of trying to impose some order on the stash, I finally decided to display it. Now I can look up from reading/grading/writing emails and get a little dose of reward. Anyone visiting me looks at the display and wonders about my sanity, not understanding how years of playing with yarn has given it the special power of making me happy to see it.
The research by Winecoff, Clithero, McKell Carter, Bergman, Wang and Huettel is focused on the role of the vmPFC in the perceived subjective value of rewards. Their study involved asking people to rate the emotional content of a range of images, some being very positive, like a cute puppy, and some being very negative, such as an infected cut [the actual pictures are kept secret so that participants in the studies have not seen them before; these examples are guesses]. They were instructed to either experience the emotional content of the image (the “experience” group) or to attempt to regulate the emotional impact of the image using a cognitive reappraisal strategy, by detaching themselves from it, or viewing it objectively as having no relationship to oneself (the “regulation” group). After giving the participants ample practice experiencing and regulating emotion, the researchers then rolled the participants into a function MRI machine in order to examine how much the vmPFC was activated. They expected that there would be a decrease in activity when a person was regulating their reaction to an image that has been deemed by many to induce positive emotion. They also proposed that there would be an increase in vmPFC activity in the regulation group when they viewed sad images, which has been demonstrated in other studies. They showed the expected results, providing some clarity regarding the role of the vmPFC. It’s not merely a brain area that is responsible for regulating emotion, but also is capable of tracking the degree to which an event or image is positive or negative.
We have all had the experience of buying yarn that we didn’t need, but it’s difficult to resist (high activity in vmPFC) when the yarn is arranged in a rainbow of colors, neatly stacked in sweater-sized piles in the yarn shop. I think that this is especially problematic for me when I go to WEBS—I have such a positive emotional attachment to that place that my vmPFC must be very active when I walk through the door, and then it goes into overdrive as I approach the warehouse in back [see this visitor’s picture], with the stacks of yarn, neatly arranged in bags. If I were in the “experience” group in Winecoff et al.’s study, I would be instructed to revel in the joy that is the WEBS warehouse. If I was in the “regulation” group, I would be instructed to consider the yarn as anyone else might see it, as something that does not relate to my interests, or as mere piles of cotton, silk, wool, and alpaca that are not important and have no specific purpose. I’m not sure the attempt to regulate my emotion would be strong enough to overcome the impact of WEBS on my wallet, but there might be some barely-detectable decrease in the activity in my vmPFC.
One idea that this research makes me consider is how can we strengthen the function of the vmPFC so that it is easier to regulate emotion? Stress can interfere with PFC function in general, so it makes sense that it is more difficult to make good choices when stress levels are high. I won’t be surprised to learn that regular exercise promotes the function of the vmPFC. I’ll look into it!