Steak or ice cream? To make the choice, the brain assigns a value to each option. For example, at dinnertime, steak may be ranked more valuable because the body needs protein, so the brain’s valuation system will respond more strongly to steak than to ice cream. But scientists have struggled with the question of how the brain integrates encoding value (how good or bad something is) and saliency (how important something is). If steak is more valuable, then it is also more salient. But what if the choice was between steak and some highly aversive food? Steak would be more valuable, but both options will be highly salient.
To distinguish between value and saliency in the brain Yale’s Ifat Levy, associate professor of comparative medicine and neuroscience, former Yale neuroscience graduate student Zhihao Zhang, and colleagues conducted a functional MRI experiment. Subjects were presented with cues that predicted various rewards and punishments (monetary gains and losses, electric shocks and pleasant images) at varying intensities. The researchers were able to point to separate brain regions that encode value and saliency. Surprisingly, said the scientists, using advanced analysis techniques, they also showed that the same area of the brain — the ventromedial prefrontal cortex — that assesses value (this is good) also retains information about category identity (this is steak). This simultaneous encoding may allow the brain to quickly update values when needed. (For example, at the end of a meal, ice cream may be rated more valuable than a second serving of steak).
More study needs to be done to understand how the brain combines these two types of information, Levy said. The study was published Dec. 4 in the journal Nature Communications. It was funded by grants from the YCCI and NIMH.