Food reward derives from nutrient content and sensory qualities

A large body of work has identified value signals in a number of brain areas and explored their role in decision-making and learning (1⇓–3). However, what is currently not well understood is how these value signals originate and how they are related to the specific sensory experiences that generate them. Taste is famously subjective and is typically treated as a given variable beyond the scope of the experiment. However, in any decision maker, be it a human or an animal, a particular pattern of sensory inputs must directly generate specific value signals in the reward circuit of that subject. This is an objective process, and, in principle at least, we should be able to understand it. Is it possible in practice? In PNAS, Huang et al. (4) describes work that starts to answer some of these questions in the domain of food preferences. Value is a fundamental concept in the behavioral sciences. Humans and animals can select between options with very different attributes. For example, we can easily choose between buying a new computer or going on an expensive vacation, even though these options are very different in type (an object and an activity) and will evoke very different sensory experiences. The behavioral sciences explain this ability by postulating an internal unidimensional signal, called “value,” that can be attributed to any distinguishable option and that collapses all attributes of that option into a single variable. This internal value signal can then be easily compared across all available options, so that the one associated with the largest value signal is chosen. While economics treats value as just a hypothetical variable that explains pattern of preference, neuroscience has demonstrated that value is, in fact, encoded in specific brain circuits. Single-unit recordings have shown the existence of neuronal activity that … [↵][1]1Email: veit{at}jhu.edu. [1]: #xref-corresp-1-1