In a new study from Johns Hopkins University, experts have identified a specific brain region that influences what we decide to eat. The researchers discovered that this part of the brain monitors our food preferences as they change across various states.
“A key function of the nervous system is producing adaptive behavior across changing conditions, like physiological state,” explained the study authors.
“Although states like thirst and hunger are known to impact decision-making, the neurobiology of this phenomenon has been studied minimally. Here, we tracked evolving preference for sucrose and water as rats proceeded from a thirsty to sated state.”
In previous work, the research team discovered that neural activity in a brain region called the ventral pallidum is related to the preference for different food options.
Using a mouse model, the researchers have now demonstrated that the same brain region tracks and updates food preferences in correlation with physiological states as they progress from extremely thirsty to satisfied.
Furthermore, when the experts targeted neurons in the ventral pallidum, they were able to manipulate food preferences.
“Your brain has to weigh different possible outcomes or options in order to make good decisions that are necessary for survival,” said study senior author Professor Patricia Janak. “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.”
Study lead author David Ottenheimer said he designed the research to investigate the relationship between the neurons in the ventral pallidum and the food choices made by the animals as their physiological state and preferences shifted.
The researchers gave thirsty rats two options they could choose from by selecting one of two levers. One lever gave them access to plain water, and the other gave them a more popular type of water with sugar in it.
“At the beginning they picked the water when they were thirsty,” said Ottenheimer. “At the end of the test when they were no longer thirsty they picked the sugar water, which tastes sweeter.”
Meanwhile, brain scans revealed that neurons in the ventral pallidum reflected the animals’ 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, which 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,” explained Ottenheimer.
In a separate trial, the researchers discovered that the ventral pallidum neurons could be artificially manipulated to shift a rat’s preference from the sugar water to the less desirable drink.
“We hypothesize that the ventral pallidum neurons that are tracking our preferences may actually be involved in forming the choices we make when faced with food decisions,” said Ottenheimer. “In the future, ventral pallidum may be a good therapeutic target to change our decision-making processes.”
According to Professor Janak, these same brain circuits are responsible for choices made in addiction. “So the knowledge we gain here can help in understanding how we prioritize drugs over other rewards.”
The study is the published in the journal Science Advances.