Researchers have discovered that a specific brain region monitors food preferences as they change across thirsty and quenched states. By targeting neurons in that part of the brain, they shifted food choice preferences from a more desired reward to a less tasty one.

The findings, published in the journal Science Advances, built upon the same team’s discovery, two years ago, that neural activity in this brain region, called the ventral pallidum, is related to the preference for different food options.

Tracking the brain
Working with rats, the researchers from Johns Hopkins University demonstrated that this same area of the brain is tracking and updating food preferences in ways that shifted as physiological states progressed from extremely thirsty to happily quenched.

“Your brain has to weigh different possible outcomes or options to make good decisions that are necessary for survival,” says Patricia Janak, senior author and Bloomberg Distinguished Professor of Psychological and Brain Sciences and Neuroscience at Johns Hopkins.

“We knew the ventral pallidum is involved in that process. Exactly how the neurons there do, that was still a bit of a mystery, especially in real-time when the best decision for you to make right now can change based on your state.”

David Ottenheimer is the lead author of the study and a former Johns Hopkins doctoral student at the University of Washington, US. He says he devised the research to determine how the neurons in the ventral pallidum related to the food decisions subjects made preference shifted due to physiological state changes.

Neural activity in rats
Researchers gave thirsty rats two options to choose from by selecing one of two levers to study the question. One lever provided plain water, the other a well-liked sugar water.

“At the beginning, they picked the water when they were thirsty,” says Ottenheimer. 

“At the end of the test, when they were no longer thirsty, they picked the sugar water, which tastes sweeter.”

Simultaneously, the team was monitoring the brain activity and found that the neurons reflected the rats’ choices for each reward.

“We saw that the neural activity when tasting the sucrose gradually increased over time, while the neural activity when tasting the water decreased. This gave us evidence that the brain signal is closely related to the change in preference as the subjects became less thirsty and were less interested in the water,” Ottenheimer notes.

Meanwhile, in a separate test, the researchers could artificially manipulate the ventral pallidum neurons to force a shift in preference from the more desired sugar water to a less desirable flavor.

“We hypothesize that the ventral pallidum neurons that are tracking our preferences may be involved in forming the choices we make when faced with food decisions,” Ottenheimer continues. 

“In the future, ventral pallidum may be a good therapeutic target to change our decision-making processes.”

“These same circuits are responsible for choices made in addiction,” Janak adds. “So the knowledge we gain here can help in understanding how we prioritize drugs over other rewards.”