At holiday buffets and pottloks, people quickly realize what dishes they should try and how much they want to eat. The neuroscientists at Johns Hopkins University have found a brain region that seems to be strongly associated with such preferences.
Researchers working with rats found robust neural activity related to food choice in a previously overlooked part of the brain. The result suggests that this brain region may be the key to developing therapies and treatments to promote a healthy diet. The findings are reported in Nature Communications
"We have found a region in the brain that reflects our perception of food in a strikingly dominant way," said lead author David Ottenheimer, a Johns Hopkins University student studying neuroscience. "The level of brain activity we saw far exceeded our expectations."
The research team wanted to know how the brain determines what and how much to eat when someone has several good food options. It's a situation that people face everyday when they are not at buffets or potlucks, then when they look over the restaurant's menus or in the fridge.
That may seem automatic when you go down to a buffet, but if you're considering either mac and cheese or mashed potatoes, the brain has to quickly figure out which of those pretty similar choices ̵
To investigate this question, researchers gave rats two similar sugary drinks. The rats preferred those made with sucrose over those with maltodextrin, and if they got sucrose, they would lick it faster.
For several days, the rats received either one drink or the other. Meanwhile, the team mapped the rats' brain activity just as the animals realized what drink they were getting, finding the nerve cells that registered the excitement of sucrose, and the disappointment of maltodextrin.
The activated neurons were in an area called the ventral pallidum, a spot that has been associated with reward and pleasure for a long time, but rather played a subordinate role.
Next, the team presented the rats with different options – either the maltodextrin drink or pure water. In this scenario, when rats received maltodextrin, they fired ventricular Pallidum neurons that they had for sucrose. This suggests that the brain area makes contextual decisions and always chooses the best food option.
"As ventral pallidum neuronal signaling changes instantly, as the rat changes its ranking, which flavor is its favorite, we see this reaction as a real-time indicator of what you like best." Author Patricia Janak, a Bloomberg Distinguished Professor of Psychology and Neuroscience.
The next step is to find out what the signaling in this part of the brain means. Is it used to reinforce previous food-seeking activities and make them more likely to re-emerge? Or is it used to influence future decisions and burden them with one food reward versus the next when someone is confronted with a food choice?
"Our data suggest that further studies of the ventral pallidum will be crucial to understanding how we make decisions about food," said Ottenheimer. "If we want to find out why one meal can be exciting in one scenario and disappointing in another, ventral Pallidum could be the key."
The research team also included Jocelyn M. Richard, a former Johns Hopkins postdoctoral fellow in Psychology and Brain Research who is now Assistant Professor at the University of Minnesota.
This work was funded by the National Institutes of Health Scholarships 5T32NS91018-17, K99AA025384, R01DA035943; a NARSAD Young Investigator Award; and the National Science Foundation Graduate Research Fellowship
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