Nick Carne
We may soon have something specific to blame for our bad food choices.
US neuroscientists working with rats have found “strikingly dominant” neural activity related to food preference decisions in a previously overlooked part of the brain, suggesting this is where those choices are made.
“The level of brain activity we saw exceeded our expectations by far,” says David Ottenheimer from Johns Hopkins University in the US, lead author of a new paper published in the journal Nature Communications.
Of course, this power could be used for good as well as evil. Ottenheimer and colleagues say their finding may be the key to developing therapies and treatments to encourage healthy eating. And that’s relevant to other issues of concern and research interest, such as portion size.
The aim of the research was to find some clues to how our brain determines what and how much to take when we have several competing food options, whether at a buffet, on a menu or simply in the refrigerator.
That often requires quick decisions about which of two similar dishes, such as macaroni-cheese or mashed potatoes, would be the most rewarding. Even if we can have both, how much of each do we take?{%recommended 7801%}
In their study, the researchers gave rats one of two sugary drinks each day; one was made with sucrose (which the rats preferred) and the other maltodextrin. They mapped each rat’s brain activity precisely at the moment it realised which drink it had been given, pinpointing the neurons that registered the excitement for sucrose and the disappointment for maltodextrin.
They found that the activated neurons were in an area called the ventral pallidum, a spot long associated with reward and pleasure perception, but thought to be in more of a secondary role.
Next, the rats were presented with a different set of options: either the maltodextrin drink or plain water. When they received maltodextrin, the ventral pallidum neurons fired as they previously had for sucrose. This suggests they were making context-dependent decisions, zeroing in on the best food option at any given time.
“Because the signalling by ventral pallidum neurons changes immediately when the rat changes his ranking of which flavour is his favourite, we see this response as providing a real-time readout of what you like best from currently available options,” says senior author Patricia Janak, also from Johns Hopkins.
The next step is to figure what the signalling in this part of the brain means. Is it used to reinforce prior food-seeking actions and make them more likely to occur again? Or is it used to inform future decisions and bias them towards one food reward over the other next time someone is presented with a food choice?
“Our data suggest that further investigation of ventral pallidum will be critical for understanding how we make decisions about eating,” Ottenheimer says. “If we want to figure out why a food can be exciting in one scenario and disappointing in another, ventral pallidum could be the key.”
