My ventral striatum made me do it

With the new year upon us, I find myself bi-directionally reflective, looking back on the research I’ve conducted throughout graduate school, while simultaneously scanning the horizon to discern what 2017 might bring.

For now, though, I’d like to distil what I’ve learned so far in my area of research: the cognitive neuroscience of self-control (and sometimes the lack thereof). Before I go on, I should say that part of the impetus to write this came from conversations with friends and family members over the holidays. I was asked about my work on several occasions, and I realized how non trivial it is to eloquently describe scientific research and why a given topic is even worth studying in the first place. Aunt Susie does not want to hear about the nuances between different regularized regression techniques. She wants to know what newfangled technologies, like non-invasive brain imaging, can tell us about her persistent hankering for Bailey’s Irish Cream that she didn’t know already.

Without further adieu, I’ll begin with a question: have you ever found yourself doing something, say getting out of your car after a local drive, and not remembering exactly how you got there? You did so safely and without consequence, that much you know. Yet certain details seem to escape you. This is not a failure of memory necessarily, but an instance of your brain efficiently organizing your thoughts and behavior so you don’t have to effortfully represent all the changing features of your sensory experiences. You were able to make that drive so effortlessly because that series of actions has become, over time, quite mundane and automatized (contrast that with a wide-eyed teen’s handling of a car during their first driving lesson). Put another way, driving to a highly familiar place has become a predictable, easy-to-execute “script,” to which you don’t have to pay much mind.

This is an example of a more general phenomenon—now a known unknown?—that has emerged from the psychological and brain sciences: much of human behavior operates outside of conscious awareness. That is not to say that human beings aren’t free agents, although this remains a hotly debated issue and very savvy thinkers have presented reasonable arguments from all sides (refer to this article series that The Chronicle of Higher Education ran a few years ago, if you’re keen to learn more). But, what seems to be true is that, more often than not, we simply are not privy to the host of factors in our external environment and subjective experience that drive our behavior.

This is especially the case with sensory cues that prompt us to eat. Enter any bakery or restaurant, and an alluring smell or quick glance at tantalizing items in a display case can subtly influence our decision on what to eat—even if we had never imagined ordering that bacon-wrapped, double-fried cheesesteak hero (with a side salad). How might such cue-driven behavior arise in the first place?

Functional neuroimaging has revealed that increased activity in the brain’s reward system, in response to appetizing food cues, can serve as a reliable marker and predictor of cue-driven responses. Indeed, work in my lab has shown that college-aged students with higher activity in the ventral striatum (a key part of the reward system; highlighted in magenta at right) subsequently gained more weight over a six-month period. In another study, activity in this same region was associated with stronger daily food desires and higher likelihood of giving into those desires and eating. Most recently these food cue responses have been studied in children (ages 9 - 12), with genetic differences modulating ventral striatum activity when kids watch food commercials.  Here is a coronal slice of the brain, with the ventral striatum (bilaterally) highlighted in magenta:

So are we at the whims of our ventral striatum, as it signals us to indiscriminately grab and eat everything in sight? Not necessarily, and I’ll hopefully tackle the difficult question “Can we increase self-control?” in a future post.

Until then, my friends, mind your P’s and (food) cues.