Anyone who works in an office knows the spot: The place where co-workers share sweet treats they brought from home, or leftovers from lunch meetings and birthday celebrations. Food appears out of the blue, and disappears just as quickly.
But why can some people walk right by the free snacks without stopping, or only go there when they’re hungry, while others can’t resist eating every time they see food there? Some may even go out of their way to pass the food-sharing spot just in case there’s something out.
Neuroscientists like Shelly Flagel, Ph.D. want to find out — and not just because of the long-term harmful effects of too many calories. The same variation between people can happen with drugs like cocaine and heroin.
For people with addiction, something as simple as passing a certain street corner can trigger a relapse in their recovery. Meanwhile, someone else might try the same drug, but not seek it out over and over again.
To find answers to questions about compulsive, repetitive seeking of substances like food or drugs, Flagel and her fellow scientists at the University of Michigan aren’t conducting studies at office food tables or street corners.
Instead, they’re peering deep into the brains of rats that have the same variation in their behaviors. And in some cases, they’re even doing something they can’t do in humans: altering the way signals travel in the brain, to see what areas play the most important roles and how much variation exists between individual rats that act in certain ways.
After years of research, they’ve gained enough knowledge to have a good sense of what’s going on, and perhaps to start to apply it to people with problematic eating or drug-taking behaviors.
Clues from chemogenetics
In a paper published recently in the journal eLife, Flagel’s team showed the importance of a tiny center in the brain called the paraventricular nucleus of the thalamus.
It acts as a kind of air traffic control tower in the brain, communicating with areas involved in everything from the drive to eat and the feeling of pleasure, to the processing of outside information from the senses.
They studied two kinds of rats: “goal trackers”, which are kind of like the co-workers who know there might be food but don’t have a problem passing up treats unless they’re truly hungry, and “sign trackers”, which are like those who can’t resist a brightly colored box of candy on the office food table, or make a special trip to the food sharing spot, just in case.
Flagel and her team used a combination of genetic engineering and a carefully delivered drug, otherwise known as chemogenetics, to ‘turn on’ the connection that allows a brain area called the prelimbic cortex to send a ‘top down’ input to the paraventricular nucleus.
In the sign-tracking rats that couldn’t resist food cues, the changes that Flagel’s team caused in the brain were enough to reduce their attraction to the cue that meant food was about to arrive. Meanwhile, the behavior of the goal tracking rats didn’t change.
Source: Thanks https://labblog.uofmhealth.org/lab-report/cant-resist-tempting-food-scientists-explore-why